Of all the musicians onstage at Saturday's epic Big 4 Festival of thrash, Dave Mustaine arrives with the most complicated history. He is an essential figure within this loud-fast genre of metal, and the originator of a certain style of guitar-shredding – first as a founding member of Metallica, then as leader of the platinum-selling Megadeth. Thrash wouldn't be the same without him.

Despite his own significant successes, his ongoing anger over being fired from Metallica in 1983 haunted him for decades, erupting during interviews and cutting wisecracks. That's finally behind him now, especially since last year's European Big 4 tour, and the four acts joining together in Sofia, Bulgaria, to perform Diamond Head's “Am I Evil?” – with Mustaine once again standing beside Metallica's James Hetfield.

In an exclusive interview, Mustaine tells the LA Weekly about the ongoing reunion of the Big 4 bands, his earliest days creating Megadeth with bassist David Ellefson, and all the scary and beautiful fans of thrash he'll see this weekend in Indio:

Even aside from the “Big 4” shows, you've been spending a lot of time on the road with Slayer.

We've gotten past all the tension of the past. It's not a secret that there was stuff I'd said a while ago – I was angry about something and I was trying to be funny. It wasn't funny to the people I was saying it about. Sometimes you tell a joke and it lands flat. Fortunately, the spirit of heavy metal heals everything with us.

Was there a rivalry between the bands?

There is probably healthy competition, but rivalry – no. We would have to be competing for the exact same core audience and playing the exact same kind of music. We're two totally different bands. Megadeth is a little jazzier, Slayer is a lot more straightforward. We both have some punk influences and were endeared by the punk audience.

Who has been showing up at your shows?

The diversity of the audiences is truly amazing. There's young and old, there's beautiful people and scary monsters. We didn't expect things to happen like this, certainly not to be this successful. I listen to kids playing guitar, and I can hear a little of my influence – and I can certainly hear the influence of what we set out to do in Metallica. We really changed the world as far as guitar playing is concerned. I know if I hadn't made that trip up to Downey that day to go audition for those guys, the world would be a different place.

You guys all started at the same time and, with thrash, created a movement that didn't exist before.

That's the thing I'm so grateful for right now. There were a lot of sour grapes in our camp for a long time. You would see all these other bands fall upward, and we would be digging in the trenches, scratching and clawing just to get a meal. Then it started to change. I guess after a period of time, if you stand for what's right and you do what's right, eventually the whole thing's going to come full-circle. I'm grateful that people even want to talk to me anymore.

Leaving Metallica and then becoming a platinum-selling artist on your own was a huge accomplishment, but your acrimony with that band seemed to go on for years.

It was a pretty big mountain to climb. The thing was, I wasn't really looking at what was right in front of me. I was looking down the road at my pals that had left me behind because the different chemical reaction that alcohol had on us. When we drank, those guys would get happy and I would get angry. I grew up fighting. My whole life I was living on the streets, scratching and clawing. I'm almost 50, and when I think back . . . David Ellefson and I had an asinine agreement: We were panhandling in Hollywood, and if we didn't make it, we were going to handcuff ourselves to a light pole and pull a hand-grenade pin and go out in a bang. Obviously we were stupid and probably stoned at the time.

You've said that performing “Am I Evil?” with all those guys in Bulgaria last year was an important moment for you.

Well, I think it was important for everybody. It was almost like a cosmic polarity thing that happened between two opposing forces. Me and James [Hetfield] were the guys that people used to always put against each other. For us to be onstage finally playing . . . The sad thing was, when they put a face to the feud, it was me against James. So when it was over, I remember hearing the audience when I hugged James and how loud they were – it was like a global sigh, like the world going, “Uhh, finally.”

Will there be another collaboration at this show?

I certainly don't know how you could eclipse that, and I know James and Lars [Ulrich] are consummate professionals and showmen. I imagine if they were going to try and do something with all of us to surpass that, it probably won't be doing a song. It will probably be doing something like skydiving onto the stage.

Tom Araya of Slayer told me he would actually be interested in doing “The Four Horsemen” [an early Metallica song originally written by Mustaine]. He said it was more representative of what you guys were all about.

Wow. On tour I've gotten to know Tom and I really like that guy. He's a really interesting and cool guy. Today I just walked in [to Slayer's dressing room] and said I heard from [ailing Slayer guitarist] Jeff Hanneman – because I texted Jeff and told him I've been praying for him about his arm and asking if he wants to talk to me. I said to Jeff, “Look, I want you to remember I had an arm injury that almost ended my career. And I know what it feels like to not be able to play.”

There were a couple of Christian protesters outside your show in Long Beach some months ago. Do you find some irony in that?

You mean the fact that they're out there picketing and I'm a born-again Christian? Well, it just shows that they don't know me. If you really want to preach the Gospel to people, you have to do it with your deeds and not your words. There's been ups and downs in my life. Everybody knows I've had a really checkered past. What better way to get me prepared to be of service to other people at the end of my career. I had a really rough beginning, but I'm having a great ending. This is all getting me prepared for what I'm going to do next.

Read more exclusive interviews with metal legends of The Big 4:

Slayer's Kerry King Reveals How Thrash Survives

Why Anthrax's Scott Ian Hates Coachella and Loves the Big 4

Slayer's Tom Araya Talks Moshpits, Spider-bites and the Big 4

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