BIRMINGHAM, England - A day-long celebration of Black Sabbath and Ozzy Osbourne began in Birmingham on July 5, as tens of thousands of fans awaited what the heavy metal legends have said will be their last live performance together.

Nearly six decades after helping pioneer heavy metal music with an eponymous song that enthralled and frightened audiences, Black Sabbath are set to return to their home of Aston for Back to the Beginning at Villa Park stadium.

Over a dozen acts including Metallica, Slayer, Tool and Guns N’ Roses are set to perform to a sea of fans in black band T-shirts with a mix of their own music and renditions of Black Sabbath numbers.

Atlanta-based rockers Mastodon kicked off the music, followed by Anthrax, Halestorm and Lamb of God. Black Sabbath are due on stage later.

The one-off gig, with profits going to charity, has been billed as Osbourne’s last performance, five years after the 76-year-old “Prince of Darkness” revealed he had Parkinson’s disease.

“The goal is a very simple one, and that is to create the greatest day in the history of heavy metal as a salute to the band that started it all,” Rage Against the Machine member Tom Morello, the music director for the event, told Metal Hammer magazine.

The gig will unite Sabbath’s original lineup of bassist Geezer Butler, guitarist Tony Iommi, drummer Bill Ward and frontman Osbourne for the first time in 20 years.

Runo Gokdemir, a teacher from London, said he had sold a car for £400 (S$696) to pay for a ticket.