|Cultural origins||Early 1980s, United States, United Kingdom and Germany|
Thrash metal (or simply thrash) is an extreme subgenre of heavy metal music characterized by its overall aggression and often fast tempo. The songs usually use fast percussive beats and low-register guitar riffs, overlaid with shredding-style lead work. The lyrics often deal with social issues and criticism of The Establishment, using direct and denunciatory language, an approach borrowed from hardcore punk.
The genre evolved in the early 1980s from combining the fast drum beats and attitude of hardcore with the double bass drumming, heavy and complex guitar style of the new wave of British heavy metal (NWOBHM). It emerged partially as a reaction to the more conventional and widely acceptable glam metal, a less aggressive, pop music–infused heavy metal subgenre which appeared simultaneously. Thrash metal was an inspiration for subsequent extreme genres such as death metal and black metal.
Four American bands— Anthrax, Megadeth, Metallica, and Slayer—are credited with pioneering and popularizing the genre, and they have come to be called the " Big Four of Thrash". The Clash of the Titans tour (1990–1991), which featured Megadeth, Slayer, and Anthrax, is considered the genre's pinnacle, after which thrash metal saw a decline in popularity throughout the decade. Thrash metal has seen a resurgence in recent times, with many of the older bands returning to their roots with their new releases. A new generation of thrash metal bands emerged in the early 2000s, drawing lyrical and visual inspiration from the older groups.
Thrash metal generally features fast tempos, low-register, complex guitar riffs, high-register guitar solos and double bass drumming.  The genre evolved in the early 1980s from combining the drum beats of hardcore punk with the guitar style of the new wave of British heavy metal.  It emerged partially as a reaction to the more conventional and widely acceptable glam metal, a less aggressive, pop-infused heavy metal subgenre which appeared simultaneously.  The rhythm guitar parts are played with heavy distortion and often palm muted to create a tighter and more precise sound.  Vocally, thrash metal can employ anything from melodic singing to shouted vocals. Most guitar solos are played at high speed, as they are usually characterized by shredding, and use techniques such as sweep picking, legato phrasing, alternate picking, tremolo picking, string skipping, and two-hand tapping.
The guitar riffs often use chromatic scales and emphasize the tritone and diminished intervals, instead of using conventional single scale based riffing. For example, the intro riff of Metallica's " Master of Puppets" (the title track of the namesake album) is a chromatic descent, followed by a chromatic ascent based on the tritone.
Speed, pacing and time-changes also define thrash metal. Thrash tends to have an accelerating feel which may be due in large part to its aggressive drumming style. For example, drummers often use two bass drums, or a double-bass pedal, in order to create a relentless, driving beat. Cymbal stops/ chokes are often used to transition from one riff to another or to precede an acceleration in tempo. Some common characteristics of the genre are fast guitar riffs with aggressive picking styles and fast guitar solos, and extensive use of two bass drums as opposed to the conventional use of only one, typical of most rock music.
To keep up with the other instruments, many bassists use a plectrum. However, some prominent thrash metal bassists have used their fingers, such as Frank Bello, Greg Christian, Steve DiGiorgio, Robert Trujillo and Cliff Burton. Several bassists use a distorted bass tone, an approach popularized by Burton and Motörhead's Lemmy. Lyrical themes in thrash metal include warfare, corruption, injustice, murder, suicide, isolation, alienation, addiction, and other maladies that afflict the individual and society. In addition, politics, particularly pessimism and dissatisfaction towards politics, are common themes among thrash metal bands. Humor and irony can occasionally be found ( Anthrax for example), but they are limited, and are exception rather than a rule.  
Among the earliest songs to be labeled thrash metal was Queen's " Stone Cold Crazy", recorded and released in 1974. The song was described as being thrash metal "before the term had been invented".  Black Sabbath's " Symptom of the Universe", released in 1975, was the inspiration for Diamond Head's " Am I Evil?".  Since then, NWOBHM bands directly influenced the development of early thrash. The early work of artists such as Diamond Head, Iron Maiden, Judas Priest, Venom, Motörhead, Tygers of Pan Tang, Raven, and Angel Witch, among others, introduced the fast-paced instrumentation that became an essential aspect of thrash.
Void is hailed as one of the earliest examples of hardcore/heavy metal crossover, whose chaotic musical approach is often cited as particularly influential.  Their 1982 split LP with fellow Washington band The Faith showed both bands exhibiting quick, fiery, high-speed punk rock. It has been argued that those recordings laid the foundation for early thrash metal, at least in terms of selected tempos. 
In Europe, the earliest band of the emerging thrash movement was Venom from Newcastle upon Tyne, formed in 1979. Their 1982 album Black Metal has been cited as a major influence on many subsequent genres and bands in the extreme metal world, such as Bathory, Hellhammer, Slayer, and Mayhem. The European scene was almost exclusively influenced by the most aggressive music Germany and England were producing at the time. British bands such as Tank and Raven, along with German band Accept, motivated musicians from central Europe to start bands of their own, eventually producing groups such as Sodom, Kreator, and Destruction from Germany, as well as Switzerland's Coroner. The Swedish punk band Warheads have also been described as a proto-thrash band.
In 1981, a Southern California band Leather Charm wrote a song entitled "Hit the Lights". Leather Charm soon disbanded and the band's primary songwriter, vocalist/rhythm guitarist James Hetfield met drummer Lars Ulrich through a classified advertisement. Together, Hetfield and Ulrich formed Metallica, the first of the "Big Four" thrash bands, with lead guitarist Dave Mustaine, who would later form Megadeth, another of the "Big Four" originators of thrash, and bassist Ron McGovney. Metallica later relocated to the San Francisco Bay Area. McGovney was replaced with Cliff Burton, and Mustaine was later replaced with Kirk Hammett. "Hit the Lights" was featured on their first studio album, Kill 'Em All, released in mid–1983. 
The term "thrash metal" was first used in the music press by Kerrang! magazine's journalist Malcolm Dome while making a reference to the Anthrax song "Metal Thrashing Mad".  Prior to this, Metallica frontman James Hetfield referred to Metallica's sound as speed metal or power metal.
Another "Big Four" thrash band formed in Southern California in 1981, when guitarists Jeff Hanneman and Kerry King met while auditioning for the same band and subsequently decided to form a band of their own. Hanneman and King recruited vocalist/bassist Tom Araya, a former respiratory therapist, and drummer Dave Lombardo, a pizza delivery driver, and Slayer was formed. Slayer was discovered by Metal Blade Records executive Brian Slagel while performing Iron Maiden's "Phantom of the Opera" at a show, and were promptly signed to the label. In December 1983, less than six months after the release of Kill 'Em All, Slayer put out their debut album, Show No Mercy.
In 1982, Stress recorded what is considered to be the first Brazilian heavy metal album.  Roosevelt "Bala" (bass and vocals) claimed this to be the first thrash metal album, since it was recorded before Metallica's Kill 'Em All. However, later he stated that some compositions have elements of thrash, like the speed, fast alternate picking, and the aggressive vocals and sound. Canada also produced influential speed metal bands such as Annihilator, Anvil, Exciter, Razor and Voivod.
The popularity of thrash metal increased in 1984 with the release of Metallica's sophomore record Ride the Lightning, as well as Anthrax's debut Fistful of Metal. Overkill and Slayer released extended plays on independent labels the same year. This led to a heavier sounding form of thrash, which was reflected in Exodus' Bonded by Blood and Slayer's Hell Awaits. In 1985, the German band Kreator released their debut album Endless Pain and the Brazilian band Sepultura released their EP Bestial Devastation. Megadeth, which was formed by former Metallica guitarist Dave Mustaine, released their debut album Killing Is My Business... and Business Is Good!, and Anthrax released the critically acclaimed Spreading the Disease in 1985.
A number of high-profile albums were released in 1986. Metallica released Master of Puppets. Megadeth released Peace Sells... but Who's Buying?, which proved to be the band's commercial and critical breakthrough and a landmark album that AllMusic cited as "a classic of early thrash".  Slayer, regarded as one of the most sinister thrash metal bands from the early 1980s, [ unreliable source?] released Reign in Blood, an album considered to have single-handedly inspired the death metal genre.  Kreator released Pleasure to Kill, which would later be a major influence on the death metal scene. 
In 1987, Anthrax released their third album Among the Living, which borrowed elements from their two previous releases, with fast guitar riffs and pounding drums. Death Angel took a similar approach with their 1987 debut, The Ultra-Violence. In 1988, Suicidal Tendencies, who had previously been a straightforward hardcore punk band, released their major label debut How Will I Laugh Tomorrow When I Can't Even Smile Today, which helped pioneer the crossover thrash genre.
Sepultura's third album, Beneath the Remains, earned them some mainstream appeal as it was released by Roadrunner Records. Testament continued through the late 1980s with The New Order and Practice What You Preach, both albums showing the band's musical growth and gaining Testament nearly the same level of popularity as the "Big Four".   Vio-lence and Forbidden, two relative latecomers to the Bay Area thrash metal scene, released their debut albums Eternal Nightmare and Forbidden Evil in 1988. Canadian thrashers Annihilator released their highly technical debut Alice in Hell in 1989, which was praised for its fast riffs and extended guitar solos. Sadus appeared later, demonstrating a sound which was primarily driven by the fretless bass of Steve DiGiorgio. In Germany, Sodom released Agent Orange, and Kreator would release Extreme Aggression.
From 1987 to 1989, Overkill released Taking Over, Under the Influence and The Years of Decay, three albums considered their best. In 1988, Slayer released South of Heaven, Megadeth released So Far, So Good... So What!, Anthrax released State of Euphoria while Metallica's ...And Justice for All spawned the band's first video, the World War I-themed song " One".
A substantial number of thrash metal groups pay tribute to punk rock and hardcore punk. Metallica has covered Discharge ("Free Speech for the Dumb"), Anti-Nowhere League ("So What?"), Killing Joke ("the Wait"), Ramones ("53rd & 3rd", among others), and The Misfits ("Die Die my Darling", " Last Caress/Green Hell"),  and Slayer recorded Undisputed Attitude, an album of punk rock covers, including Minor Threat, early DRI, and Iggy and the Stooges.  Megadeth have covered two Sex Pistols songs (" Anarchy in the UK" and "Problems"), as have Anthrax (" God Save the Queen" and "Friggin' in the Riggin"). Anthrax have also covered "Protest and Survive" by Discharge on their album Attack of the Killer B's, " We're a Happy Family" by Ramones, and "New Noise" by the Swedish band Refused as a hidden track on Worship Music. Overkill have covered the Sex Pistols (" No Feelings"), Ramones (" I'm Against it"), and Dead Boys (" Sonic Reducer", and "Ain't Nothing to Do"). In addition, Pantera covered Poison Idea ("the Badge"). 
A number of more typical but technically sophisticated albums were released in 1990, including Megadeth's Rust in Peace, Anthrax's Persistence of Time, Slayer's Seasons in the Abyss, Suicidal Tendencies' Lights...Camera...Revolution!, Testament's Souls of Black, Kreator's Coma of Souls, Destruction's Cracked Brain, Forbidden's Twisted into Form, Exodus' Impact Is Imminent, and the more groove-oriented Pantera's Cowboys from Hell. All of those albums were commercial high points for the aforementioned artists. Many of these bands embarked on a group tour called the "Clash of the Titans" the same year. Several albums that continued this style, which had come to be known as technical thrash metal, were released in 1991, such as Overkill's Horrorscope, Heathen's Victims of Deception, Dark Angel's Time Does Not Heal, Sepultura's Arise, and Coroner's Mental Vortex.
Later in 1991, Metallica released their eponymous album, known as "The Black Album". The album marked a stylistic change in the band, eliminating much of the speed and longer song structures of the band's previous work, and instead focusing on more concise and slower songs. It would go on to become the band's best selling album, and began a wave of thrash metal bands releasing more commercially oriented albums.
After the commercial and artistic climax for the genre, the energy of the thrash metal was exhausted and it was overtaken by the rising alternative metal and grunge movements.  In the 1990s many veteran thrash metal bands began changing to more accessible, radio-friendly styles.  Metallica was a notable example of this shift, particularly with their mid–to–late 1990s albums Load, and ReLoad, which displayed minor blues and southern rock influences, and were seen as a major departure from the band's earlier sound.  Megadeth took a more accessible heavy metal route starting with their 1992 album Countdown to Extinction,  and Testament released the melodic The Ritual in 1992. 
As further extreme metal genres came to prominence in the 1990s ( industrial metal, death metal, and black metal each finding their own fanbase, the heavy metal "family tree" soon found itself blending aesthetics and styles.  For example, bands with all the musical traits of thrash metal began using death growls, a vocal style borrowed from death metal, while black metal bands often utilized the airy feel of synthesizers, popularized in industrial metal. Today the placing of bands within distinct subgenres remains a source of contention for heavy metal fans, however, little debate resides over the fact that thrash metal is the sole proprietor of its respective spinoffs.
Many 1980s-era thrash bands who split or were inactive during the 1990s – such as Dark Angel, Death Angel, Nuclear Assault, and Forbidden – reunited in the 2000s. Notable bands returned to their roots with releases such as Metallica's Death Magnetic (2008), Megadeth's Endgame (2009), Slayer's World Painted Blood (2009), Exodus' Exhibit B: The Human Condition (2010), Anthrax's Worship Music (2011), Overkill's The Electric Age (2012), Testament's Dark Roots of Earth (2012), and Flotsam and Jetsam's Ugly Noise (2012).
Thrash metal is directly responsible for the development of underground metal genres, such as death metal, black metal  and groove metal.  In addition to this, metalcore, grindcore and deathcore employ similar riffs in their composition, the former with more focus on melody rather than chromaticism. The blending of punk ethos and metal's brutal nature led to even more extreme, underground styles after thrash metal began gaining mild commercial success in the late 1980s.  With gorier subject matter, heavier downtuning of guitars, more consistent use of blast beat drumming, and darker, atonal death growls, death metal was established in the mid-1980s. Black metal, also related to thrash metal, has emerged at the same time, with many black metal bands taking influence from thrash metal bands such as Venom.  Black metal continued deviating from thrash metal, often providing more orchestral overtones, open tremolo picking, blast beat drumming, shrieked or raspy vocals and pagan or occult-based aesthetics to distinguish itself from thrash metal. Thrash metal would later combine with its spinoffs, thus giving rise to genres like blackened thrash metal and deathrash.    
Groove metal takes the intensity and sonic qualities of thrash metal and plays them at mid- tempo, with most bands making only occasional forays into fast tempo,  but since the early 1990s it started to favor a more death metal–derived sound.  Thrash metal with stronger punk elements is called crossover thrash. Its overall sound is more punk-influenced than traditional thrash metal, but has more heavy metal elements than hardcore punk and thrashcore. 
Thrash metal emerged predominantly from a handful of regional scenes, each of which was generally distinguished by the unique characteristics of its bands.
- Bay Area thrash metal: In addition to being the most commercially successful, San Francisco Bay Area thrash tended to be the most progressive and technical of the major regional thrash scenes, being strongly NWOBHM influenced. Metallica, Testament, Exodus, Death Angel, Vio-lence, and Forbidden are prominent examples of bands to emerge from this region.
- East Coast thrash metal: Centered in New York City, the East Coast's thrash metal tended to display a sound that incorporated a strong hardcore punk influence. An emphasis was placed on aggression and speed rather than technicality. Anthrax, Overkill, Nuclear Assault, Toxik, and Whiplash exemplified the style to emerge from this regional scene.
- British thrash metal: The British thrash bands leaned towards a more traditional heavy metal approach, often heavier though less aggressive than their American counterparts. The most notable bands from this scene are Onslaught, Xentrix, and Sabbat.
- Brazilian thrash metal: The Brazilian thrash scene is notable for producing a handful of bands that would become principal parts of thrash metal's prevalence in the early 1990s. There were three scenes where Brazilian thrash metal was originated: Belo Horizonte (the most prominent), São Paulo, and Rio de Janeiro. The most famous bands from this scene are Sepultura, Dorsal Atlântica, Executer, Chakal, MX, Korzus, and Sarcófago.
- Teutonic thrash metal: The German and Swiss region spawned dozens of bands since the mid-1980s that developed its own style. The most prominent bands from this scene are Kreator, Destruction, Sodom, Tankard, Coroner, Holy Moses, and Exumer.
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