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The best celebrity sex videosGrammys did what no one else ever has: Silenced Metallica lead singer James Hetfield.

Metallica and Lady Gaga took the stage on Sunday night for a duet made in Hell -- and I mean that in the best possible way -- that isn't much of a stretch, really, given Gaga's hard-rock roots. She was dazzling, of course, blowing out some goddess-level metal vocals and striking all the badass rock-poster poses.

But microphone problems marred the performance's early goings: Hetfield's signature growl was absent from the mix as the band's new single "Moth Into a Flame" got raging, and for a couple of verses, it was clear that his mouth was moving -- but nothing was coming out.

Someone fix James Hetfield's mic! pic.twitter.com/YXA3ADsKAw

— Mashable (@mashable) February 13, 2017

No matter. For one thing, Gaga -- who in a previous life was known around Greenwich Village as the killer hard-rock busker Stefani Joanne Angelina Germanotta -- is a super-pro singer and dancer, and had plenty of momentum coming off her spectacular Super Bowl performance to hold her own.

And when Hetfield realized he wasn't in the mix, he just doubled up on Gaga's mic, Bruce Springsteen-style.

Good enough for rock 'n' roll, as they say:

Hetfield doesn't need your broken mic, #GRAMMYs, Gaga has him covered pic.twitter.com/smWuOltZx6

— Mashable (@mashable) February 13, 2017

Doesn't mean he was happy. As the fiery performance concluded, Hetfield sulked over to the side of the stage and angrily tossed his white ESP guitar over into a stack of amplifiers.

It was the second sound snafu of the night, after Adele's tribute to George Michael had to be re-started, presumably because of a problem with her earpiece monitor.

Let's just say no one wants to be sitting in on that post-show production debrief.