Last night, several of the world's most celebrated musicians joined forces at the Key Club in Hollywood, Calif. for the third installment of the Metal Masters series.

The concert/clinic featured Kerry King and Dave Lombardo (Slayer), David Ellefson (Megadeth), Charlie Benante and Frank Bello (Anthrax) and Mike Portnoy (Adrenaline Mob/Flying Colors), all performing at various points throughout the night

If that lineup wasn't already killer enough, Phil Anselmo (Down, ex-Pantera) and Geezer Butler (Black Sabbath, ex-Heaven and Hell) both made surprise appearances, leaving all in attendance with their mouths agape.

Anselmo treated the packed club to ripping versions of Slayer's "Raining Blood" and "Angel of Death," before breaking into "A New Level," "Mouth for War," "This Love" and "Walk." Butler then got on stage and joined the all-star band through Black Sabbath's "Hole in the Sky."

Watch the metal dream team perform "Hole in the Sky" below the cut.

Watch Metal Masters Perform "Hole in the Sky"

The Metal Masters event was presented by musical instrument giants Samson, Hartke and Zoom and Best Buy.