During its 27-year history, Megadeth has produced 12 studio albums -- some that have gone on to become thrash-metal classics, some of which the band and its fans might want to forget.

One that is not up for debate is 1990's "Rust in Peace," which benefited from frontman Dave Mustaine's newfound sobriety and the addition of former Cacophony shredder Marty Friedman. With its blistering metal fury and songs about politics and war, "Rust in Peace" won critical acclaim, platinum sales, Grammy nominations and loads of respect.

Twenty years later, it hasn't gathered a lot of rust, as Megadeth will demonstrate Friday night at the Palace Theatre when the band plays it straight through. It's a fairly unusual move considering that Megadeth just released the well-received "Endgame" in September. The band planned to renew that campaign as part of the "Carnage Tour" with Slayer and Testament, but Slayer bassist Tom Araya hurt his back, postponing that tour for later in the year.

"We had this big block of time," says Megadeth drummer Shawn Drover, "so we decided to tour America once again and we wanted to do something a little different, and coincidentally this is the 20th anniversary of 'Rust in Peace.' We got [bassist] Dave Ellefson back in the band. We thought what a great thing to offer people, just this one exclusive tour leg doing this record. Fans are just tripping out on it."

The drummer, a Megadeth member in good standing since 2004, says the band has had about half of "Rust in Peace" in its set lists for years, so the tour required just learning about five songs. It's undoubtedly been the most work for guitarist Chris Broderick, who replaced Mr. Drover's brother in 2008.

"Chris can pretty much nail all of Marty's solos," the drummer says. "It's so close it's ridiculous. He's just really got that flair for emulating other guitar players. In this band, our fans are so critical of that and anything we do in terms of performance. We have to make sure we're on the ball and we're lucky that Chris can step in and nail those solos note for note."

A revolving-door policy has been a fact of life for Megadeth in its 27-year career. There's even a wiki page devoted to the band's 19 former and four current members. Perhaps no situation is more bizarre than Mr. Ellefson's, considering that the original member filed a royalties lawsuit (unsuccessfully) against Mr. Mustaine in 2004, and, now, with things patched up, he has rejoined the band for this tour. The drummer is thrilled to hold down the rhythm section with him.

"When I joined the band back in 2004, it's something I hoped for when the initial call came out. It wasn't meant to be at the time, but it worked out and everyone's just ecstatic that he's back in the band now. He fits like a glove."

In light of Megadeth's long roster of ex-members, should we conclude that Mr. Mustaine, who was famously booted from Metallica, might be a little hard to work with?

"I've never had a problem with Dave," the drummer says. "I can't speak for anybody else. For me, we're similar in a lot of ways as to what we want in the band. We want this band to excel to the highest degree. I always want us to do better today than we did yesterday. That's the mind-set. I'm not some 21-year-old little punk who just wants to get wasted and become a morphine junkie and hang out with all these chicks. I'm about to be a grandfather in a couple months. I'm not a spring chicken here. My job is to play drums for Megadeth and keep the integrity of this band intact."

Mind you, the drummer is not exactly grandpa age at 43. The same year he hits that phase of his life he'll be all over the world with Megadeth, including a landmark Big Four tour, in Europe, with fellow thrash pioneers Slayer, Anthrax and Metallica. It will obviously require a few hatchets to be buried.

"We haven't played with Metallica yet," he says. "As far as I'm concerned, everything's fine. If there was a problem, I don't think this would have happened. A lot of time has passed since this [stuff] went down years ago. It was 1983. That's all water under the bridge, we're all a little older and wiser. Again, we're just looking forward to the first time this is happening in our careers."

The Big Four tour comes at a time when the nu metal bands from the past decade have faded somewhat and people are turning back to old-school thrash.

"At the height of grunge, saying you were in a metal band was like telling people you had leprosy," Mr. Drover says. "People just didn't want to hear anything about it and it really went back underground. Starting about 2000, it slowly came out of the trenches again. Here in 2010, things have really come full circle now where it's celebrated that these bands are still intact a quarter century later. I don't know any band that can stay at the apex of popularity year in and year out. It goes through peaks and valleys, but the fact that all these bands are still here now and most of those nu meal bands or whatever you want to call them have disappeared, it's just a testament to this genre of music."

Critics Andrew Druckenbrod and Scott Mervis talk about music on "The Beat," available exclusively at PG+, a members-only web site of the Pittsburgh Post-Gazette. Our introduction to PG+ gives you all the details.