For four consecutive albums, Metallica relied on the talents of producer Bob Rock, a man who has worked with the likes of the Cult and Mötley Crüe over the course of his nearly 30-year career. The guys came to trust Rock after he'd helmed their 1991 self-titled breakthrough, and they even recruited him for their three subsequent follow-ups: 1996's Load, 1997's Reload and 2003's St. Anger.

But in 2006, Metallica revealed that their 15-year relationship with Rock had dissolved and that they'd be searching for a new producer for [article id="1592244"]their forthcoming ninth LP, Death Magnetic,[/article] which hits stores September 12. They found what they were looking for in Rick Rubin, one of the most important producers of the last 20 years, who has worked with artists as diverse as Slayer, the Red Hot Chili Peppers, Neil Diamond, Weezer, Rage Against the Machine and Jay-Z.

At the start of the studio sessions, frontman James Hetfield said Rubin challenged them to think back to 1985, when they wrote and recorded 1986's Master of Puppets. He wanted Metallica to return to that mind-set, to recall those elements, experiences and influences that drove them to what's widely acknowledged as their finest work.

"For us to accomplish that mission, we needed to shed a lot of extra baggage," Hetfield said. "We needed to focus a little more, we needed to make quicker decisions, we needed to be OK saying no to certain stuff, and we needed to weed through stuff quicker."

Rubin wanted to break the habits Metallica had developed under Rock's watch and wanted them to track Death Magnetic in a much different way.

"One of the coolest things was Rick actually suggested that we all stand up and rock out, like we would live," said [article id="1592114"]bassist Robert Trujillo[/article]. "And we did, and it put a lot of life into the basic tracking of it all. It was almost to the point where, when I was retracking stuff, I was standing up, headbanging. I'd never done that in a recording situation before. He's a great song doctor, and he has great ears."

According to guitarist Kirk Hammett, Rubin's style was drastically different than Rock's, in that he was less hands-on. In fact, he was barely ever in the studio.

"The great thing about working with Rick is he's never around," he said. "I would say that's a very strong point, in that it leaves the four of us to take on the entire brunt of the work and the planning that goes into the songwriting process and the recording process. Of course, Rick was there for part of that process -- when we recorded drums and vocals -- but the fact that we were isolated in our studio, working on the songs ourselves, made a big difference, because it kept our sound pure. We got more Metallica that way than we had previously with Bob Rock.

"Bob would add a lot of his own musical input, and with that came a lot of his own influences and style and jurisdiction and idiosyncrasies," Hammett continued. "And it would eventually make it into our sound. But with Rick, because he wasn't there, it's almost 100 percent undiluted Metallica. He'd come in and say, 'That's good, that isn't, change that.' And we would have to figure that out for ourselves. This is the most pure we've sounded in a long time."

Hetfield agreed that while Rock was a solid producer, Rubin's style is dramatically different.

"Rick is not the kind of producer like a Bob Rock, who's there every moment, holding your hand, making you step up," he said. "[Rock] arranged everything, all the time, and wore many hats in the studio. Rick Rubin? No hat. Rick comes in and goes, 'Well, where's the songs? OK, that's good. That's not so good. More of this, less of that -- see you in a few months. Goodbye.' And that's what we needed -- that brutal honesty, to get through it, and it worked."

Metallica said it was Rubin's past efforts that attracted them to him as a producer, because they wanted a tighter, more in-your-face result. And that's what they got with Rick.

"The Slipknot that he did, the System of a Down records he did, and even the Johnny Cash stuff, where it's the essence of him, and you hear him, you hear what's going on -- that's what I want, I want people to really hear Metallica," Hetfield explained. "So, in a way, it's [got] somewhat of an older sound. Songs and arrangement-wise, we've got a lot more diversity on the record -- instrumentals, fast, shorter songs, epic, ballady moments. It's quite different from St. Anger, where if you're angry, this is your album, and if you're not, it might take some work."

So what was the hardest thing about working with Rubin on Death Magnetic?

"Letting go," Hetfield said. "Letting Rick produce. It's not luck -- he's got something, he's not stupid. He knows what will be best for us, I believe that, and we had to trust that process. That was difficult, because Lars and I have been driving this band forever, and to back off a little bit, that was hard."