Dominic Cooper has a short resume in theater and film, but it is nonetheless impressive, and with his brooding good looks he just may be the next British heartthrob to make it big in the United States.

After all, Cooper was the object of desire in "The History Boys" and co-stars with Keira Knightley in the forthcoming movie "The Duchess." And now, he can be seen as the adorable and buff fiance Sky in the movie adaptation of "Mamma Mia!," the popular musical that features the songs of ABBA.

"I don't think I'm handsome," Cooper says by phone from Berlin, where he attended a premiere of "Mamma Mia!" the night before. "I look like a root vegetable on the screen. Wait until you see 'The Duchess.' I wear the most ludicrous wigs — next to Keira, I look like a turnip."

Although Cooper, 30, believes he is lacking in the looks department, the only root in his future right now will be from his fans.

Cooper first came to the attention of Americans when he played Dakin in Alan Bennett's Tony-winning play "The History Boys," adapted for the screen in 2006. He also made a splash as Willoughby in Masterpiece Theatre's "Sense and Sensibility" and played opposite Scottish actor James McAvoy in "Starter for 10." But "Mamma Mia!" is the first movie he'll appear in that has big box-office possibilities and worldwide notice, as well as a star-studded cast headed by Meryl Streep, whom Cooper said had a big influence on him.

"When you stop learning is when you stop being in the theater," Cooper said. "You just learn such a great deal from her. How Meryl tries things out is just fantastic. She explores the text in a way to make it work in her favor.

"So does Richard Griffiths," Cooper adds, referring to the star of "The History Boys." "They make it so natural."

In "Mamma Mia!" Sky is engaged to Sophie (Amanda Seyfried of "Big Love"), who is trying to find out which of three men (Pierce Brosnan, Stellan Skarsgard and Colin Firth) is her father. Sophie, pretending to be her mother, Donna (Streep), sends wedding invitations to the three men. Donna's two best friends (Christine Baranski and Julie Walters) also come to the Greek island, where the wedding will be held at Donna's inn.

Throughout the film, directed by Phyllida Lloyd, best known for her work in theater and opera, the music of ABBA is integrated into the story line. At first, Cooper was concerned about singing and dancing — he almost didn't audition because of that — but found out he wasn't alone.