Very few bands can claim to have been as influential as these Birmingham giants. The group formed in the UK's second city when guitarist, Tony Iommi, and drummer, Bill Ward, decided to form a blues band. The band recruited two local musicians, Terence Michael "Geezer" Butler and John Michael "Ozzy" Osbourne, from the band Rare Breed, to round out their lineup. The band chose the name Earth, and after a brief stint in Jethro Tull, Iommi returned to Birmingham with a new sense of purpose for his young group. Around that time, the group changed their name to Black Sabbath (because of the existence of another British group called Earth), a reference to Boris Karloff's horror film that was showing across the street from their rehearsal room.
The quartet released their 1970 dark debut, Black Sabbath, which many consider to be the first heavy metal album. While the record is openly blues-inspired, it was heavier than anything else before it, and though it was a decidedly dark record, it achieved commercial success, selling over a million copies. They followed it up with the staggering Paranoid, which set the standard for all heavy metal to come, featuring some of rock's most essential, transcendent tracks ("Paranoid," "War Pigs," "Iron Man"). Though Iommi's menacing riffs drive the record, Butler and Ward form a rock-solid rhythm section that perfectly complements Osbourne's frenzied, impassioned vocals.
Follow-ups Master of Reality in 1971 and Vol. 4 in 1972 continued to refine their intimidating formula to increased commercial success—both records sold in excess of a million copies and reached the Top Ten in America and the UK. Sabbath became considerably more ambitious both lyrically and musically with their fifth album, Sabbath Bloody Sabbath (1973), one track featuring keyboards from Rick Wakeman of Yes. However, Sabotage sold much less than its predecessors upon release in 1975, and the following two records, Technical Ecstasy and Never Say Die!, would be the last two to feature Osbourne before he quit in 1979 to pursue a solo career.
Osbourne would be replaced by Ronnie James Dio, singer of Rainbow, with whom they recorded 1980's Heaven and Hell, a strong seller and the emergence of Black Sabbath Mach II. Ward left the group, replaced by Vinnie Appice on drums, and this line-up recorded Mob Rules, but Dio would depart the group two years later, replaced by Ian Gillan of Deep Purple. Gillan would feature on 1983's Born Again, which performed well in the UK, but Gillan exited to be replaced briefly by Dave Donato. Osbourne would perform with the group at Live Aid in 1985, but after Butler left the group, Iommi would be the only original member to continue the band as a vehicle for his own recordings. During the next several years, there would be a smattering of reunion moments, most notably the Reunion double-disc set recorded by the original line-up in 1997 and toured in 1999 before headlining Ozzfest, Osbourne's touring music festival, in 2001.
Their raw, down-tuned sound coupled with ominous lyrics and imagery created the template for what heavy metal would become. They were a direct influence on metal's most influential bands, such as Slayer, Metallica, and Celtic Frost, boasting a legacy that's made them rightfully known as the "Godfathers of Metal."