Back in the day, back when a Big 4 show was nothing but a fanboy's dream, three of the most important thrash metal bands of all time teamed up for a monumental tour called Clash of the Titans. The US version of the trek featured Megadeth, Slayer and Anthrax as rotating co-headliners, playing huge venues across America in 1991, still part of the Rust in Peace era to Megadeth fans.

In interviews at the time, Megadeth leader Dave Mustaine was often asked which band he thought benefitted the most from the tour. His response included three simple words: "Alice in Chains." Yes, when Death Angel reportedly had to turn down the opening slot, the Clash of the Titans organizers turned to a then-little-known Seattle band who had a tough time warming up the thrash-friendly crowds.

Alice in Chains weren't the only band to go on to massive heights of fame and fortune after supporting the world's "state of the art speed metal band," as Megadeth was often billed. Stone Temple Pilots found themselves in the same position in 1993. A few years before their gold-selling Obsolete, in 1995, Fear Factory joined a Megadeth bill that also included a new band called Korn. From Coal Chamber to Machine Head, the list of Roadrunner luminaries alone who've supported Megadeth is astounding.

With the 2012 edition of the Mustaine-curated Gigantour rolling out January 26 with a badass undercard consisting of Motörhead, Volbeat and Lacuna Coil, we're taking a look back down "The Killing Road" at some of the coolest 'Deth openers from within our own catalog.

KORN (1995)
FEAR FACTORY (1995, 2005)
Megadeth's "Reckoning Day 1995" lineup: Korn, Flotsam and Jetsam, Fear Factory. Yes, as Megadeth toured supporting Youthanasia, they assembled a package that began with Fear Factory, who were promoting the groundbreaking Demanufacture. They were preceded by Flotsam and Jetsam, the Arizona thrashers best remembered as the band Jason Newsted played in before Metallica. And first up, there was Korn, who had somehow managed to combine Faith No More, broken childhoods and Bakersfield, California with who knows what else, creating a brand-new sound that changed heavy music both artistically and commercially for years to come. Jonathan Davis broke out his now-signature bagpipes during that tour.

"At the time, no one knew where to put us, so we were doing tours with KMFDM to Megadeth [to] Pennywise," Davis told Explore Music in an interview last year. Fear Factory came back to join Megadeth on the first ever Gigantour a decade later.

COAL CHAMBER (1997)
LIFE OF AGONY (1997, 2005)
DEVILDRIVER (2007)
During the glory years of nu-metal, Fear Factory guitarist Dino Cazares helped make the Roadrunner A&R team aware of the L.A. band Coal Chamber, who released their eponymous debut in February, 1997. About a year later, Coal Chamber went on tour with Megadeth, who were supporting Cryptic Writings, which had spawned the rock radio hit "Trust."

Coal Chamber's first album, one of the definitive releases of the nu-metal subgenre, eventually went gold in the United States. Years later, following subsequent Coal Chamber albums that further explored the band's darkly Gothic undertones, frontman Dez Fafara returned to Roadrunner with the ferocious extreme metal band DevilDriver, who toured supporting Megadeth as well.

"I've had the pleasure of touring with Megadeth a few times in my career,” recalls Fafara. “I must say that in my case, both bands were treated with kindness and respect and taken care of well. But here is something you don't expect from one of the biggest rock stars of our time. On the second night [of Megadeth/Coal Chamber], as I was walking in the building, I slipped on some ice. At first I tried to laugh it off, but as I stood up, I realized that something bad had happened to my ankle: it was horribly twisted.

"It wasn't broken, but it was not good and it was swelling fast. I hobbled backstage to ice it and was doing so for an hour before the show. A half hour before Coal Chamber took the stage, in walks Dave Mustaine. He kneels down and says, 'I heard you messed up your ankle pretty bad. Let me look at it.'" Dez says that Mustaine "sent out for some holistic ointment" and 15 minutes later he was back, personally wrapping the astonished singer's ankle himself. "[Mustaine] told me to try and have a good show. His kindness that day meant the world to me and now, 13 years later, I'll never forget it! Thanks, Dave, for being a brother."

Life of Agony opened the tour that featured Coal Chamber, and rejoined Megadeth in 2005 on the first Gigantour.

DREAM THEATER (2005)
Dream Theater also played the inaugural Gigantour in 2005, which featured Anthrax (on a separate leg), Fear Factory, Dillinger Escape Plan and Nevermore, two members of whom were in Sanctuary, whose debut album was produced by Mustaine back in the day.

Shawn Drover, who took over drum duties in Megadeth in 2004, continues to feel a strong personal connection to his current labelmates. "I have a lot of great memories from all the Gigantour tours Megadeth have done and having my friends in Dream Theater on G1 is certainly one of them. Progressive metal is something I really enjoy, as the level of musicianship—and certainly in the case of Dream Theater—is very high. To be able to pull off live what they have recorded over the years is something I marvel at, for sure."

Dream Theater’s then-drummer, Mike Portnoy, joined Megadeth onstage on September 3, 2005 at the Toronto Gigantour stop. He got behind the kit for "Peace Sells...," with Shawn switching to guitar. As revealed on the subsequent Gigantour DVD, Portnoy dumped baby powder on the snare before he left the stage. As soon as Drover started playing "Holy Wars...," the powder blew all over his face.

"Great band, great guys, end of story," Drover says.

OPETH (2006)
Dave Mustaine and Mikael Åkerfeldt certainly have a lot in common. They both sing, they both play guitar, they've both fronted monumentally game-changing metal bands and they have both navigated lineup changes and changing times while maintaining a vision as creative bandleaders that has ensured each man's musical legacy. The pair finally shared a touring bill together in 2006, when Opeth took part in the second Gigantour alongside Lamb of God, Arch Enemy and Overkill.

SOULFLY (2006)
Max Cavalera is a heavy metal legend in his own right, from the noisy thrash of early Sepultura to the landmark Arise album, the hugely influential Chaos AD, the hugely influential all over again Roots and continuing through to his eight albums fronting Soulfly along with all of his other projects. Despite his own iconic status, he still counts Megadeth as a major inspiration to him.

"I still love the classics like Megadeth, Slayer and all those bands that are still playing now with kick-ass shit after twenty or thirty years," he told MetalSucks.net last year. "That's awesome that those bands are still playing. It makes me really proud and makes me want to continue playing because it's an inspiration that those bands are still going."

Also, did you know David Ellefson played bass on nearly half of Soulfly’s 2004 album, Prophecy? He was still a few years away from rejoining Megadeth, though, when Soulfly were added to the Australian edition of Gigantour in 2006.

MACHINE HEAD (2007, 2009, 2011)
Bay Area metal warriors Machine Head have toured with Megadeth on several occasions, including as direct support on Megadeth/Slayer, on the 2011 Rockstar Mayhem Festival tour, and when both supported Heaven & Hell, aka Black Sabbath with the late Ronnie James Dio.

In 2009, speaking about The Blackening touring cycle, Machine Head's Robb Flynn told About.com: "We got to tour with a lot of our idols. We did Slayer and Megadeth, we did six months with Metallica... There were some huge moments for us."

Shawn Drover is quite fond of Flynn and his crew as well, calling them "definitely one of my favorite heavy metal bands of today."

"We have played a ton of shows with Machine Head since 2007, which was great for me as I am friends with all those dudes," Drover says. "One of the great things about Machine Head is that they completely have their own sound. I have not heard one band that sounds like they do, which in this day and age, seems rare. They are a very consistent live band as well."

Gigantour 2012 kicks off this Thursday, January 26; visit our tour page to find a show near you!