In 1968, four guys in Birmingham started a band together: Singer Ozzy Osbourne, guitarist Tony Iommi, bassist Geezer Butler, and drummer Bill Ward. At first, they called themselves the Polka Tulk Blues Band. They changed their name a couple of times, first to Earth and then to Black Sabbath. Under that final name, they released a string of absolute monster classic records and more or less invented the genre of heavy metal. Osbourne left the band in 1977, and he went on to a great solo career, while the other guys made more great records with their next singer, the late Ronnie James Dio. The four original members of Black Sabbath have reunited a few times over the years, and now they’ll do it one more time, for what’s billed as Ozzy Osbourne’s final performance.