PRYOR — The fourth-annual Rocklahoma music festival proved that sunscreen and going shirtless are as much a part of the rock ‘n’ roll experience as a band cranking its guitar amps to 11.

Braving the scorching sun, Three Days Grace and Godsmack joined 15 other “heavy rock” bands inside a 400-acre outdoor venue on Friday.

And they brought friends.

Heather Clark, of Alva, Okla, listens to Janus perform during Rocklahoma Friday, May 28, 2010, in Pryor, Okla. Photo by Miranda Grubbs, The Oklahoman

The town’s population will swell thanks to camping opportunities and headliners ZZ Top and Tesla playing today and Sunday.

But the Memorial Day weekend festival drew more than beer tents and diamond-studded belts to Pryor.

Rocklahoma was established in 2007 as an exhibition strictly for ’80s “hair metal” acts, but promoters expanded the line-up this year to include rock genres from the past four decades.

Former Warner resident Jerry Jones drove 920 miles from Deming, N.M., and said he enjoyed the festival changes.

“They’re gonna have to keep doing that to keep the younger generation sucking in,” he said. “That’ll keep it alive for a long time.”

Jennifer Smith, of Oklahoma City, grew up with ’80s “hair metal” bands.

“We like the newer bands too,” Smith said. “It brings kind of a younger crowd, which is fine if you’re over 21, but I left my kids at home for a reason.”

But Anna Shorey of Cleveland, OK, didn’t. Shorey said she woke her son at 6 a.m. to be the first waiting outside the chained Rocklahoma entrance alongside dozens of eager fans.

First on the main stage was Las Vegas native Adelita’s Way. The quartet has toured with Three Days Grace and shared festival bills with many Rocklahoma acts.

Janus drummer Johnny Salazar, performs during Rocklahoma Friday, May 28, 2010, in Pryor, Okla. Photo by Miranda Grubbs, The Oklahoman

“It’s been a day of hanging out with our friends,” said lead singer Rick DeJesus. “It’s a good experience, a lot of good people and diehard fans. It’s fun.”

Adelita’s Way didn’t have any trouble filling the massive main stage with its heavy alternative rock, prompting cheers from a horde of sweaty fans. And neither did Buckcherry, who proudly blared songs that would need several bleeps for radio play.

Texas band Black Tora got a second chance Friday to play Rocklahoma because in 2008 storms wrecked its stage. Lead singer Chris Daniel wasn’t afraid to channel ’80s rockers and tossed his shirt at listeners before finishing his set.

Pryor Mayor Jimmy Tramel said he expects rowdy behavior from crowds but welcomes Rocklahoma patrons.

“I’m going out there to have a good time,” Tramel said. “People around here are not used to seeing some of the (tattoo) ink all over them, earrings with the long hairdos and stuff like that.

“For the most part, we look at them say ‘This is Rocklahoma weekend.’ That’s what we do.”