When heavy metal and hardcore punk collided in the late seventies, it was largely under the influence of the New Wave of British Heavy Metal. The resultant alloy was thrash. The core bands were mostly American: Metallica, Anthrax and Slayer all formed in 1981. The style spread worldwide, however, with German band Sodom and Brazil’s Sepultura leading the furious charge. Essentially a faster, louder, meaner version of the heavy rock that preceded it, thrash hit the mainstream with Metallica’s self-titled 1991 album that topped the charts. There is often an anti-establishment tone to the lyrics while a thudding double-bass drum sound and fearsome guitar parts define the sound.