Lady GaGa's Metallica Grammys duet came about after she got chatting to Lars Ulrich at Bradley Cooper's house party.

The 30-year-old pop superstar is gearing up to perform with the heavy metal band at this year's ceremony at the Staples Center in Los Angeles on Sunday (12.02.17), and has shared how their idea to perform together was sparked from a conversation she had with the group's 53-year-old drummer at the 43-year-old 'American Sniper' actor's home.

She shared: ''[I] was at Bradley Cooper's house with Lars Ulrich, and we were just, like, hanging out ... ''

The 'Million Reasons' hitmaker didn't give away any more information about her performance with the 'Enter Sandman' group - also comprised of James Hetfield, Kirk Hammett and Robert Trujillo - but she has high hopes as the last time she saw them at a gig they were ''better than they've ever played before''.

Gaga told Zane Lowe on his Apple Beats 1 Radio show: ''I've got to tell you something: I went to see Metallica live.

''I mean, I've seen them live recently, and we were watching the how and I'll tell you something, those guys play better than they've ever played in their whole lives.''

The 'Nothing Else Matters' rockers previously teased they have something ''unique'' in the pipeline for the slot at the prestigious bash.

They said: ''We promised you something unique for Grammy night and we are absolutely thrilled to confirm that Lady Gaga will be joining us on stage.

''It was a total honour to be nominated, but now this?''

Metallica have been nominated for Best Rock Song for 'Hardwired' - from their latest LP 'Hardwired... To Self Destruct'.

Gaga hasn't been nominated because her latest record 'Joanne' isn't eligible as it wasn't released between October 1, 2015 and September 30, 2016.