Look out for long hair and the sign of the devil. Heavy metal is back.

After all but disappearing from the mainstream, hard rock is making a comeback, with new bands reinventing the genre and old bands touring, rereleasing albums and even making new ones.

"Kids are into Lamb of God, Korn and Godsmack," MTV2 Programming Executive Alex Coletti said, naming some currently popular metal bands. "Their parents are going to Def Leppard to hear the hits. And Ozzfest (search) is multigenerational — families can bang heads together."

MTV, which will debut a new version of the 1987-1995 program Headbangers Ball (search) on its MTV2 channel this Saturday, is on top of the trend.

"People were always asking me to bring back the Ball," said Coletti. "And there's so much good new metal coming out. Kids needed a place they could count on [to see and hear it]."

But it's not just kids listening to metal. According to Ian Christe (search), author of the recently released Sound of the Beast: The Complete Headbanging History of Heavy Metal, metal fans fall into three groups.

"I think a third of it is nostalgia, people in their 30s that have money for shows. A third of the audience never stopped listening to metal and didn't even know it went out. And a third are the young people getting into music for the first time," he said.

Kids are more likely to be banging their heads to next-generation metal bands like Slipknot, Linkin Park and System of a Down than to Motley Crue, Anthrax and Judas Priest, and the new Headbangers Ball will reflect that fact.

"We're not going to play hair bands circa 1989 for two hours," Coletti said. "We'll always throw back to the older videos — those classics that inspired the new bands — but you'll be more likely to see Staind, Korn and The Datsuns."

However, older bands seem to have sensed that the time was right for a comeback.

Members of Ratt and Judas Priest have regrouped. Metallica, who will host the first episode of the new Headbangers Ball, has a new album on the way. And Universal recently rereleased all of Motley Crue's records.

Ozzfest, the heavy metal festival named for former Black Sabbath front man and MTV dad Ozzy Osbourne, is still going strong. Whitesnake just wrapped a tour with the Scorpions, and Def Leppard is currently on the road.

"Almost every [metal] band that ever recorded is together now in some form," Christe said.

New metal is both similar to and different from old metal. Slipknot maintains old metal's fascination with the dark side, wearing bondage outfits and pincushion masks. The band Cradle of Filth is into vampires and witch imagery like face paint and black candles.

But hair, while still long, is no longer "big," Christe said. And "you don't hear grand hymns to Satan anymore," he added.

So why metal now? Coletti attributed its resurgence, in part, to the current mood of the country.

"Look at where the world is. Music is louder and harder in trying times," he said.

Christe said it could be that bubblegum music is once again dying out.

"Pop music kind of has a three-year cycle," he said. "Sometimes metal bands play to 50,000 people, sometimes 5,000, but metal never completely goes away. Once in a while it bumps into the mainstream, as it seems to be doing now."

But that doesn't mean that Britney Spears can't stay relevant.

"She just needs to learn to play electric guitar," Coletti said.