Public opinion was always going to be divided when Metallica and Lady Gaga teamed up at the Grammys this week but one thing was certain — James Hetfield was PISSED after technical difficulties resulted in the frontman's mic not working for the duration of the performance. 

Footage of the iconic singer visibly frustrated at the end of the set soon hit the internet and, according to Blabbermouth, the stuff-up was reportedly caused by a stagehand who accidentally unplugged Hetfield's mic.

Appearing on The Late Late Show With James Corden yesterday, Metallica drummer Lars Ulrich confirmed that Hetfield was indeed "livid".

"In the heat of the battle, you're out there and you're playing, when it's a technical issue, you don't really know — 'Is it going to the house?' 'Is his vocals going to the truck? 'Maybe it's just the monitors.' — so you've just gotta keep playing," Ulrich explained.

"We get off stage, we get back there, and I haven't seen [James] like that in twenty years. I mean, he was livid. He's aged really well and he's a pretty chill guy, but the first five or ten minutes in that dressing room was not a lot of fun. 

"But, like they say, the show must go on, and we fought through it. And with the fire and Gaga in my lap for about a minute at one point, it was just, 'Keep going, keep going, keep going.' So we fought through it, and a lot of people said that at least it made for great television, which is really the point of doing the Grammys to begin with."

See footage of the Grammys performance below.