Black Sabbath stalwarts Ozzy Osbourne and Geezer Butler joined Metallica on stage as part of their 30th anniversary celebrations.

Metallica are commemorating the career milestone with a series of special gigs at the Filmore, San Francisco.

And, as NME reports, the Black Sabbath duo, who have recently reformed the band, joined Metallica on stage last night (December 10) to play classic Sabbath tracks 'Iron Man' and 'Paranoid'. Bassist Geezer Butler also teamed up with Metallica to play 'Sabbra Cadabra'.

Ex-Metallica guitarist and current Megadeth mainman Dave Mustaine also joined his old bandmates in a historic rendition of some of the band's early material.