Sandra Oh Debuts at the Met Opera in ‘La Fille du Régiment’

“It’s happening,” Sandra Oh said as she exited her dressing room at the Metropolitan Opera. “I’m doing this.”

She was guided through the Met’s backstage, past pieces of sets for “Turandot” and “Don Giovanni,” smiling and saying hello to people she had met in recent weeks while preparing to make her opera debut as the Duchess of Krakenthorp in Donizetti’s “La Fille du Régiment,” which begins its run of seven performances on Friday.

Oh paused briefly in the wings, then stepped onstage. She had stood there before, but at the final dress rehearsal on Tuesday, she was appearing before an audience for the first time. And when she made her entrance, the people roared.

The Duchess, a speaking role, is sometimes performed by retired singers. But it is also used as an opportunity for appearances by celebrities: actresses, like Kathleen Turner, the drag queen Monét X Change and even Ruth Bader Ginsburg.

Oh has made a name for herself onscreen, with starring roles in the TV series “Grey’s Anatomy” and “Killing Eve,” as well as movies including “Sideways” and the newly released “Good Fortune.” But lately she has also become a fixture onstage, performing most recently as Olivia in “Twelfth Night” at Shakespeare in the Park this summer.

At the opening of “Twelfth Night,” she ran into Peter Gelb, the Met’s general manager. They had met in the 1990s, when they were both working on the movie “The Red Violin” (Oh as an actor and Gelb as an executive at Sony). He invited her to play the Duchess in “La Fille,” and because a movie project had been postponed, she was free. It helps that, having grown up in Ottawa, she speaks French.

But until recently, Oh had never seen the mechanics of opera, the sheer number of people and different departments it takes to put on a show, which can impress even someone used to Hollywood productions.

“I love seeing all the stuff backstage,” she said. “It’s like, ‘Turandot’ is over there, ‘La Sonnambula’ is over there, and there are all these pieces, but also so much hard work and professionalism going on all the time. It’s all happening at an extremely high level, down to the person in charge of the calendar.”

She had no idea before coming to the Met. “It’s a great ignorance on my part to think that somehow it all magically happens,” Oh said. “But that’s also the beauty and the mystique of the performance. You don’t see any of the effort, only the beauty.”

Most of all, Oh said, she has been in awe of operatic voices up close. Her character is haughty and quick to bark in anger. She wears a perpetual scowl, which hasn’t been easy to maintain when hearing the soprano Erin Morley or the tenor Lawrence Brownlee.

“It’s one of the hardest things,” Oh said. “Erin’s singing is, like, this beautiful goddess coming down, and I just have to be filled with anger and hate. All these unbelievable singers, and I have to look like a big sourpuss.”

She started coming to the Met in early September, during the run of “Twelfth Night,” for costume fittings. Rehearsals began a couple of weeks ago, bringing her together with the cast and allowing her to get acquainted with the Met’s immense stage and auditorium. Unlike performing onscreen, or even in most theaters, opera requires broad gestures capable of reaching the farthest seats.

For that, she said, she has received advice from Met veterans who told her to aim her sound “at the exit signs.” She has also gotten help backstage, from the “total pros” who work on costumes, wigs and makeup; one even made her a large fan, inspired by a prop from “Twelfth Night,” that she waves with ferocity to signal the Duchess’s personality in her performance.

There is a lot of character built into her costume: a lacy dress with a comically large bustle, a blond wig with a streak of purple and a cartoonish hat, connected to the wig with magnets, with Kathleen Turner’s name tag still inside. Oh held up her left hand, coated with rings while she got ready for Tuesday’s rehearsal with the help of the dresser Laila Alvarado and Lexi O’Reilly, a wig-maker and hair stylist. Occasionally, Oh would pause for a drink from a water bottle she brought from “Twelfth Night,” decorated with stickers of her castmates, including Daphne Rubin-Vega as a beagle.

When she left her dressing room, she hardly looked like a guest. Affable and quick to hold a door open for others, she joked around with her colleagues before heading to the stage. (During a photo shoot with the cast, she dramatically waved her bustle around, trying to find room.) When she made her entrance and the audience cheered loudly, the bass-baritone Peter Kalman said from the wings, “That’s it, we can go home.”

Oh’s performance will be new to many of her fans, with pantomime comedy and an artful lack of subtlety played for laughs. “Everything has to be slower, and more deliberately carved,” she said. “The way that I would normally do comedy is to drop a line, but you cannot do that here. You have to kind of lob it up, in a different way.”

At the dress rehearsal, she got plenty of laughs, especially when she broke out of her French dialogue to say in English, “Sweetheart, don’t be stingy with the schnitzel.” Her castmates congratulated her afterward, and on the way out, Brownlee told her she had done great. But Oh knew that she wasn’t quite finished getting ready.

“I’m still trying to figure stuff out,” she said. “You know, I have seven chances, so I’m going to make the most out of all of them.”