Watch Zac Brown perform a little Black Sabbath with the Foo Fighters

The Foo Fighters are currently taking over The Late Show with David Letterman with a week-long residency and last night none other than Zac Brown joined the group for a little metal jam.

Cool.

Check out the Zac, Dave Grohl, and the rest of the Foo Fighters performing Black Sabbath's War Pigs together.