Foo Fighters team with Zac Brown to cover Black Sabbath on Letterman

For the first of five nights playing “Late Show With David Letterman,” the Foo Fighters brought with them a special guest to cover a very special song.

Dave Grohl and co. drafted the help of their pal Zac Brown (who appears on their upcoming album “Sonic Highways”) for a faithful cover of Black Sabbath's seminal anti-war anthem “War Pigs.”

With the addition of roots rocker Brown, the performance features no less than four guitars, but they still can't measure up to the de-tuned menace of Sabbath axeman Tommy Iommi.

The vocals are performed by both Brown and Grohl (if you can see him behind all that hair), but likewise can't replicate Ozzy Osbourne's original performance.

Still, they're clearly having one hell of a fun time. 

Watch it here:

Fun fact: “War Pigs” has also been covered by bands like The Flaming Lips, Faith No More, Cake and Quasi.

“Sonic Highways,” which was recorded in multiple U.S. music capitals (including Brown's Nashville studio), will be released November 10. A documentary about the album premieres on HBO on October 17. 

Hear more about the project from Grohl:

What surprises do the Foos have in store for the rest of their Letterman week?