Melissa Etheridge Says She’s ‘Having A Blast’ As She Steps Into Broadway’s ‘American Idiot’

Melissa Etheridge says she’s having a “blast” getting in touch with her punk side.

The Grammy- and Oscar-winning singer-songwriter will play drug dealer St. Jimmy in the hit Broadway musical based on Green Day’s rock opera, “American Idiot.”

“It’s been crazy. Oh my God, it’s so fun, though,” the folk rocker says. “I’m having a blast. I’m so outside of my comfort zone and I’m like living out high school fantasies.”

Etheridge, 49, takes over the part from Green Day’s lead singer Billie Joe Armstrong for eight shows, from Tuesday to Sunday. Armstrong, the composer and co-author of the musical, returns Feb. 10 as part of a 50-show stand.

The high-octane show follows three working-class characters as they wrestle with finding meaning in their lives. One joins the Army and is deployed to the Middle East, one becomes a father and struggles with domestic life, and one descends into a drug-fueled life in the city — thanks to St. Jimmy, a sort of charismatic dark angel originally written for a man.

Etheridge, best known for her songs “Come to My Window” and “I’m the Only One,” first saw the show at the St. James Theatre on 44th Street over Thanksgiving and was initially hesitant when producers suggested she might want to join the show.

“When they called me, at first I was like, ‘Aw, no. That’s really nice, but no,’” she recalls. “Then I kind of sat with it for a couple of days and thought, ‘This could be supercool and superfun.’”

Michael Mayer, the show’s director and story co-writer, says Etheridge has made the part her own during rehearsals. “It shakes everything up sonically from what we’re used to hearing, which is really wild,” he says. “She sounds beautiful on it, and haunting and there’s a very different emotionality that she brings to it.”

While Etheridge says singing the new songs, including “Know Your Enemy” and “Last Night on Earth,” isn’t too much of a stretch — “It’s all up in my rockin’ screaming range,” she says — the physical work of performing has been an adjustment.

“To get up there on stage without a guitar in front of me is the first sort of fear barrier I had to get through,” she says. Learning the show’s choreography, she acknowledges, was next and it was probably the hardest part: “I never had to use that part of my brain — singing and then moving at the same time with a lot of other people. If you mess up, you’re gonna get trampled.”

For the past few days, she’s been soaking up the show and chatting with Armstrong. “What a sweetheart and what a talent,” she says. “I’m a Green Day fan, but I haven’t gotten inside the songs the way I have now and I really appreciate his talent very, very much.”

Etheridge, who will tour Canada after her shows to support her latest album, “Fearless Love,” is also getting a thrill from being in the same theater where “Hello, Dolly!” ‘‘Oklahoma!” ‘‘The Producers” and “Tommy” were staged.

“Being a part of that is really thrilling,” she says.

Etheridge, who is writing her own Broadway musical, says her debut on the Great White Way has given her new credibility with her two older children, Bailey Jean and Beckett, who are huge fans of the show and Green Day.

“My daughter was listening to it over and over. You know how when a 14-year-old gets something, they listen to it all day and all night? So I started to know these songs and just from osmosis got more familiar with it,” Etheridge says.

“Then when the offer came in, I went, ‘OK, how can I tell my daughter I said no,’” she says, laughing. “And, of course, it made me instantly cool with her, which is hard to do with junior high kids.”