Prior to scoring fame as a member of Slayer, guitarist Kerry King enjoyed a brief stint in Megadeth.

The tenure occurred in April of 1984, just a few months after the release of Slayer’s debut album Show No Mercy. The guitarist was in Northern California when a mutual friend connected him with Megadeth.

"We were looking for a second guitar player to do these gigs when we debuted the band in 1984 up in San Francisco,” David Ellefson, Megadeth’s bassist and co-founder, recalled during an appearance on Todd Kern’s YouTube channel. “And he came in. At that time, Slayer still had makeup. Slayer didn't really have their identity yet.”

Almost immediately, the bassist was blown away by King’s prodigious talent. “He would stand there with just no expression on his face and watch Dave [Mustaine] play some gnarly riff like 'Chosen Ones' or 'The Conjuring',” Ellefson explained. “And then [King] put his hand on his guitar and played it back note for note. And you're, like, 'Holy hell! This guy really gets Dave.'”

“I was an admirer of Mustaine, 'cause I saw Metallica play with Mustaine,” King revealed in a 2010 interview with Artisan News Service. “I was blown away by how good that kid was.”

King played roughly five shows with Megadeth before returning to Slayer and his Southern California home.

Watch Kerry King Playing with Megadeth During a 1984 Performance

"It's funny, because when Kerry played with us, he would still wear his Slayer colors. We didn't, so we would be there with high-tops and sneakers on and Kerry would be there with nails for days everywhere,” Mustaine recalled. “We had a great time, man. He's a really smart player and he was able to learn the stuff that I wrote really quickly.”

Despite their shared musical respect, the relationship between King and Mustaine went through trying times, with the rock rivals often airing their dirty laundry in interviews. Much of the animosity stemmed from 1991’s Clash of the Titans tour, a trek which featured Slayer, Megadeth, Anthrax, Alice in Chains and a lot of behind-the-scenes tension.

For decades, the two traded insults. In 2005, following comments from Mustaine questioning King's talent, the Slayer rocker referred to Megadeth's frontman as a “cocksucker,” calling Mustaine a “miserable person.”

Despite these feelings, Slayer and Megadeth would join forces for the 2010 American Carnage tour, and later, the vaunted "Big 4" performances.

By 2015, things had lightened slightly. In a conversation with Loudwire, King fondly remembered his brief stint with Megadeth. “It was good time back then,” the guitarist admitted. “[Mustaine] was cooler back then. I think there’s been a lot of drugs and extracurriculars between now and then,” King went on to opine. The Slayer rocker then threw in an additional barb, saying that he didn’t understand “how anybody can be in Megadeth for more than a couple of hours, because that guy’s crazy.”

“We’ve had a very up-and-down relationship over the years, because, as you know, Kerry is very outspoken, and sometimes he’s joking about somebody and sometimes he’s not,” Mustaine explained in a 2018 interview with Rock and Roll Garage. “But he’s been a great friend, and I have tremendous respect for what Slayer’s done.”

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