Kerry King joined King Diamond onstage during the Rockstar Energy Drink Mayhem Festival at the PNC Bank Arts Center in Holmdel, N.J., on Tuesday night (July 21). The Slayer guitarist joined the band for an energetic rendition of Mercyful Fate's 1983 classic “Evil.” Watch the fan filmed video in the player above.

Both Slayer and King Diamond are out on the Rockstar Energy Drink Mayhem Festival, so it seems like it was only a matter of time before there was some sort of "A tale of two Kings" collaboration. Kerry King is a long time fan of Mercyful Fate and King Diamond, who are known for their original and progressive black metal. At the end of the raucous version of “Evil,” Diamond gushed to King saying, “What an honor, thank you so much!”

King Diamond recently sat down with Full Metal Jackie to discuss the Mayhem Festival and his legacy and how he has influenced so many current metal bands. “It’s great to hear,” Diamond said. “I was very honored the other day, I went and saw my friends in Volbeat play in Dallas. Anthrax was supporting. I met Scott Ian before, but I met all of them this time around and got to really talk to them. What an amazing bunch of guys, really great human beings and nice people. It was amazing.” He continued, “They were also talking about like, 'Hey! Let’s do ‘Am I Evil.’ 'Okay, I can do ‘Evil’ in my sleep so we can do that if you want to,' and then one of the other guys was like, 'Hey there’s a little more to it than just that [laughs] it can quickly go wrong if you haven’t tested it properly. So we’ll do it another time.' I remember, the drummer said that he could play the entire Melissa album if need be. It’s nice to hear that people are really into that old music still.”

Meanwhile, Kerry King recently criticized the Mayhem Festival organizers after co-founder Kevin Lyman said the metal genre was becoming “gray, bald and fat.” King responded, “Whoever booked this tour made a gigantic error.” He also called the outing a “glorified Slayer show.” He concluded, “I understand it from a fan’s perspective. I wouldn’t spend money to come to this either.” The guitarist also stated that not only might this be the final time Slayer play the Mayhem Festival, it also might be the final Mayhem Festival ever.

The Rockstar Energy Drink Mayhem Festival also features Slayer, Hellyeah, The Devil Wears Prada and more. The tour rolls into Bristow, Va., on Friday, July 24. Check out all the tour dates here.

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