Yesterday, we found out that Katy Perry was pencilled in to perform at this weekend's Grammy Awards - but another special collaboration is on the cards, too.

A week after her well-received Super Bowl show, Lady Gaga - no stranger to a collaboration - will play at the biggest night in music with rock band Metallica.

Gaga, of course, played the Grammys last year too, when she paid tribute to David Bowie.

The news was rumoured after a fan site posted a clip (below), but Rolling Stone later confirmed it was true.

The question is, will she guest on a Metallica song, or will James Hetfield and co. put their metal spin on one of hers?

The Grammys take place this Sunday at the Staples Center in Los Angeles.