VIDEO: Zac Brown, Foo Fighters cover Black Sabbath on Letterman

Georgia native Zac Brown joined Dave Grohl and the Foo Fighters last night on "Late Night With David Letterman" for a face-melting cover of Black Sabbath's "War Pigs." It was the first night of the Foos' week-long residency on "Late Night" to promote their new album and documentary, "Sonic Highways."

A Brown-Grohl pairing might seem perplexing, but the two have actually been working together since last year, when Grohl produced the Zac Brown Band EP "The Grohl Sessions, Vol. 1." Grohl a song from the EP, "Day for the Dead," with the band at the 2013 Country Music Association Awards.