Pop superstar Lady Gaga will perform with METALLICA at this year's Grammy Awards. She just did the halftime show for the Super Bowl! No one knows what song they're going to perform yet, but the show is happening! Metallica is up for the Best Rock Song category for their newest track "hardwired". I'm a giant lady gaga fan...I can't wait to see what they come up with! If you could pick a pop star to duet with a legendary rock group, who would it be?