In the early ‘80s, while rock was pushing toward post-punk and New Wave, the forces of metal were on a collision course. The classic heavy metal practiced by Black Sabbath and their descendents converged with the progressive energy of the New Wave of British Heavy Metal, and the two were met head-on by the speed and ferocity of punk. In this perfect storm, thrash was born. The fast, chugging chords and wailing solos of Metallica began to define the genre’s sound, while Megadeth inherited the cleaner vocals and more proggy twists and turns of groups like Iron Maiden. Slayer channeled darkness into songs about suicide, Satanism, insanity, and murder, pushing thrash into a violent new territory. Going forward, thrash would continue to be transformed by the leaden riffs of Sepultura and the breakneck speeds and white-noise screams of Pantera. Bands like Power Trip are keeping thrash alive with their churning, distorted guitars and guttural growls.