Skillet is definitely cooking on both burners.

The Memphis band has made a successful crossover into the mainstream and active rock charts while still keeping a strong foothold in its Christian music roots.

"Once a band crosses from Christian music to mainstream music, once they've had one or two hits, they kind of stop doing Christian music," said John Cooper, the band's lead singer, bass player and lone original member.

"And I'm not saying every one of them, nor disrespectful towards anyone's decisions, but they start to do less and less in the Christian market," he added. "Skillet has kept doing what we've always done."

While Skillet shares the headlining bill with Third Day for a spring tour, which hits the iWireless Center in Moline on Sunday night, it spent the latter part of 2013 on a European tour opening for Nickelback.

Founded in 1996, Skillet signed with mainstream Atlantic Records in 2003, but did not get a song on mainstream radio until 2009 with "Hero."

Although the band's albums sold well and got Christian radio airplay, Cooper said he was holding out hope the band would become a rock success as well.

"It used to hurt us that we were so vocal about being a Christian act in the mainstream world," he said in a phone interview from a tour stop in Philadelphia. "They didn't understand that. Now it's something people respect about us, that we never forgot where we came from."

The 38-year-old Memphis native said he didn't have to make a choice of one genre or another.

"I've just refused to stop doing Christian music because I love it and I believe it and I grew up with it," he said. "They are the people who brought me here.

"I always wanted to do both. I never just wanted to do Christian music, but I wanted to sing about my faith. It was something we tried to wait and see if doors would open," he continued. "We tried to get some interest in a mainstream label partner, but that didn't happen for a long time, and it was a lot of work."

Skillet made a breakthrough in 2006, thanks to social media. The then-burgeoning website exposed the act to new listeners, whether they were Christian music fans or not.

Unlike some of the other acts on the active rock charts, Skillet has lyrics that can be heard and understood.

"Skillet does have a unique quality in that we're hard rock, but extremely melodic. It's musical, and it's a little bit poppy in the melodies, but the guitars are heavy. It's that very thing that makes Skillet unique, and, I think, hurt us in radio for a long time because it was different," Cooper said. "Now I think it's the reason things are going good. It finally caught on, you know?"

Whether it's a Christian band or not, Skillet pulls off another rarity — performing as a four-person, co-ed band, including Cooper's wife, Korey, on rhythm guitar and keyboards. Lead guitarist Seth Morrison and drummer Jen Ledger round out the band.

"You don't see a lot of girls that rock really hard. There's a bunch of really talented girl musicians. They just don't play in hard-rock bands," Cooper said. "That was one of the things we saw at first because it really is a man's world."

The Coopers bring their two children on the road with them, he said, which prevents the need for going back home and spending time with the family, a constant reprieve for musicians.

Cooper said he admires his wife for pulling off family and music duties on the road.

"She's the reason this works. She likes to be in the background, and she doesn't need a lot of credit and doesn't want to do interviews or be the center of attention," he said.

"I have that kind of natural lead singer thing where I have to have attention or I freak out."