It was true clash of the metal titans when Philip Anselmo joined Slayer to perform a live rendition of a Pantera classic in Greece. That's too much metal awesomeness for one stage. Headbangers, it's Slaytera.

Slayer frontman and bassist Tom Araya prefaced the performance by saying that everyone needed to offer well wishes to the birthday boy, and he even played some of the melody of the song, since Anselmo turned 45 on June 30.

Anselmo also exchanged some pleasantries with the band while on the stage. "As a young man growing up with f---ing heavy metal, listen to this, close, never in my f---ing life did I ever think I'd be on the same stage as f---ing Slayer," Anselmo said. "I'll say this. Slayer has never needed me for f---ing nothing. You know what? I needed Slayer." He continued, barking in drill sergeant fashion, "Do you understand me? I needed Slayer." Yes, sir!

He then introduced the 'Vulgar Display of Power' hit 'F---ing Hostile,' saying, "You might have heard this song before. If you know it, sing it like your f---ing a--hole is on fire." Anselmo followed with the Slayerized version of the Pantera classic -- a true extreme metal hybrid! Makes you jealous of the Greek metal fans that got to enjoy this live and in the flesh, right?

Anselmo even endeavored to hug Araya during the solo, while he was still playing his instrument. The singer also rubbed guitarist Kerry King's head while he shredded.

We'll borrow a phrase from Wayne and Garth from 'Wayne's World' to describe this metallic mashup of an iconic band and equally legendary frontman: "We're not worthy!"