Video: Lady Gaga and Metallica perform together at the Grammy Awards.

As advertised, Lady Gaga joined Metallica onstage at the Grammys tonight, performing "Moth Into Flame," a track from the latest Metallica album, Hardwired...To Self-Destruct." Notably, James Hetfield's microphone seems to have malfunctioned for the first portion of the performance. Video footage can be found below.