Thrash developed in the early Eighties as a subgenre of the broader heavy metal category and gained momentum throughout the decade. From the pioneering “Big Four” bands—Metallica, Megadeth, Slayer and Anthrax—to Exodus, Testament, Overkill and Sepultura, thrash metal pushed the boundaries of aggression, speed and stamina with fast, muted open-string-based riffs and furious lead breaks.