One of extreme metal's most influential bands, Celtic Frost took the blisteringly raw sound of thrash in radical new directions on albums like 1985's To Mega Therion and 1987's Into the Pandemonium. Adding elements of goth, industrial and classical music to their full-throttle assault, the genre-bending Swiss band stood apart from their peers while also inspiring the bands who would create death metal and black metal. Following an ill-fated flirtation with glam metal, Celtic Frost split in '93, but returned heavier than ever with the doom-inspired riffs of 2006's Monotheist.