Update: The dress rehearsal for the performance has been uploaded to Lady Gaga's official VEVO channel! Watch below... Earlier: Lady Gaga has delivered another spectacular Grammy performance. Hot on the heels of her incredible Super Bowl Halftime show, Gaga joined rock legends Metallica at this year's Grammy Awards for a fiery duet on "Moth Into Flame," a single from their latest album. "You know how the Grammys like to have their duets thing and when it was suggested that La