While Slayer shows are amazing, it looks like there's a lot of fun to be had during soundcheck as well. During a recent stop in Bonner, Mont., Behemoth frontman and current Slayer tourmate Nergal got a chance to front the group during a performance of Slayer's "Evil Has No Boundaries."

Nergal seemed to be thrilled by the opportunity, beaming throughout as Kerry King offered blistering guitar work while Tom Araya and Gary Holt flanked him, often playing off the killer drumming from Paul Bostaph as well. While fan-shot footage of the performance can be seen above, Nergal himself posted some footage online with his own personal account via Instagram. See his comments and the posting below:

"Evil has no boundries" - That's the song my affair with Slayer has begun ages ago. I must have been 8 or 9 years old I guess when I heard it on a pirate cassette. Didn't know much of an English language so we would sing whatever we hear. And the word EVIL reminded us how PIWO (beer) sounded phonetically! We would f--k around and sing "PIWO!!! PIWO!!! PIWO!!!" instead until years later when we realised its meaning. The word EVIL would eventually be the key word to define my whole career with the band on so many levels and beyond. When I told that story to Kerry and Gary they were like: Let's do it! We r in!!! I already knew the lyrics by heart and here I am... sharing the stage with one of the best bands on the planet in one of my favorite songs! Dunno how I'm gonna top it but that's not the case now. Living the f--kin' dream and enjoying the f--k out of it.

Meanwhile, Nergal wasn't the only one getting in on the fun. As Slayer rocked a cover of AC/DC's "Dirty Deeds Done Dirt Cheap," Nergal and Lamb of God's Randy Blythe joined in from the side of the stage with backing vocals. Watch that Instagram post below.

Slayer, Lamb of God and Behemoth will wrap up their summer tour tonight in Phoenix.

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