Galas are supposed to be fun, and maybe glamorous, but not distinguished, musically. The Metropolitan Opera has never gotten that memo. Or at least that has been my impression, over the years. Some of my best evenings at the opera have been on Met opening nights. And Monday was none too shabby.

The Met opened its season with three acts from three different operas, staffed with some of the finest singers in the world, all led by James Levine. Probably that’s the main reason the Met galas aren’t throwaways: They’re led by Mr. Levine, who would not countenance a mediocre musical evening, even if the patrons are in their most expensive clothes.

He began, as always on opening night, with the national anthem, conducted in his usual way: straightforward, graceful, stirring. And he continued with Act I from Mozart’s “Marriage of Figaro,” which begins with a piece perhaps as famous as the national anthem: that overture. In it, he was just as in the anthem. Also, he did not hurry the piece, and he pays extraordinarily close attention to the dynamics in it.

Serving as Figaro was Bryn Terfel, the beloved Welsh bass-baritone. He poured his personality into it, as well as his vocal skills: He was fairly big voiced, yet accurate, Mozartean. His two arias – “Se vuol ballare” and “Non piu andrai” – were unusual: They bristled, and Mr. Levine drove them with unapologetic muscle. About the only complaint you could make about Mr. Terfel was that he was sharp on a few high Fs. It perhaps had to do with a determination not to be flat.

Also pouring on personality was the soprano Isabel Bayrakdarian, who sang Susanna. For years, I have called her “delectable,” and her delectability quotient on this evening was through the roof. You could hardly take your eyes off her, and her singing was clear, musical, and assured.

Susan Graham was Cherubino, and gave her big aria – “Non so piu” – a rare theatricality. It was pulsing, alive, imaginative. And yet it was not wrongly personal. Dwayne Croft did his usual solid job as the Count, and Michel Senechal performed his usual Don Basilio: It keeps the audience in stitches. Peter Rose and Wendy White teamed for Dr. Bartolo and Marcellina, and they were professional and likable, as expected.

What we had, here, was seven singers reveling in their considerable talents. They were unmistakably happy to be onstage. But most important of all was the Mozart sense of Mr. Levine – that meaty, robust, masculine Mozart that is not so far from Beethoven, at all. And that has the requisite feminine as well.

The gala continued with Act II of Puccini’s “Tosca,” in which Mr. Terfel again appeared – as Scarpia, of course. I have long had reservations about him in these bad-guy roles, because his essential good-guyness manages to peek out. Call it a handicap. Still, he made a snarling Scarpia, almost Gobbi-esque at times. And he was superb in his seductive passages. One line that stands out is neither snarling nor seductive. It is a simple, terrible question: “Ebben …?” In other words, “Will you or won’t you, Floria Tosca?”

The Cavaradossi was a new tenor on the block, Marco Berti, whose instrument was gleaming, and whose diction was super-crisp. He produced effortless volume. In fact, his cries of “Vittoria!” may have been the loudest sounds in the Metropolitan Opera House since Birgitt Nilsson last said hello.

And portraying Tosca was Angela Gheorghiu, the Romanian soprano who is – no getting around it – one of the best singers in the world. Critics and other dubious characters love to hate her, somehow. That is an analysis for another day. Anyway, she is an excellent Tosca, combining fire and tenderness. Her “Vissi d’arte” on Monday night was not without problems: She had trouble finding the first note, and her last note was flat, for about half of its (long) duration. (I’m talking about the first half.) And the notes in between? She sold the aria decently, but she can do better.

But back to Mr. Levine: Here again he was the key player. He made Puccini’s score jump off the page, pointing up the unpredictability – the sheer weirdness – of it. This performance buttressed me in my belief that Puccini is one of the most underrated of composers, however popular he is with the public.

Closing the evening was Act III of Saint-Saens’s “Samson and Delilah,” starring the Samson of our time: Placido Domingo. For about 10 years now, I’ve called him “the ageless Spaniard,” and although he sometimes makes you doubt, he did not, on this occasion. He was in splendid form. When it seemed he might falter, he hung on. Opposite him as Delilah was Denyce Graves, who was not in her best voice: She was a bit strident and raspy. But there’s no doubt she knows the role. Frederick Burchinal, the High Priest, was manful and steady.

The Met’s production of “Samson and Delilah” is by Elijah Moshinsky, and it is one of the best productions the company has: groaning with sensuality (among other things). The dancers danced up a storm, and the Met orchestra did the same. One should not leave out the Met chorus, either: It sang beautifully as well as wildly, and showed particular control in the mezzoforte range.

But I should say a further word about the tenor, Mr. Domingo: Has there ever been such a pitiable, such an overwhelming, Samson?

Really, it’s no secret why these opening nights are successful: Repertory is well-chosen, singers are well-chosen – Mr. Levine is in the pit. In this house, a gala performance is more than pre-dinner entertainment.