Yannick Nézet-Séguin with the Met Orchestra at Carnegie Hall. Photo: Richard Termine

After a few years adrift, the Metropolitan Opera has found its sheriff — or maybe shepherd is a better word. Yannick Nézet-Séguin has just completed his first season as music director (although the transfer of power in the classical-music world can be a weirdly slow and fitful ritual). He skipped opening night last September; delegated the spring’s keystone event (Wagner’s four-opera “Ring” cycle); and conducted just four performances of one slightly arcane French opera (Pelléas et Mélisande), three of another (Dialogues des Carmélites), and a run of La Traviata. Only with an exhilarating postseason concert with the Met Orchestra at Carnegie Hall did he finally change the name on the door: This is his house now. Even so, he will come back for just three of the 25 operas on the company’s docket for 2019–20.

The change is worth the frustration. In the ten years since Nézet-Séguin, then in his mid-30s, made his Met debut, he has racked up a solid list of canonical operas there, including overpowering performances of Parsifal and Elektra. If there are weak spots in his repertoire, he has yet to give us a glimpse. Any lingering doubts about his talents vaporized in the first moments of Debussy’s La Mer at Carnegie Hall on June 3, when unstoppable forces coursed beneath the pretty glints and glimmers on the surface of the sea. Throughout the concert, Nézet-Séguin rested his fingers lightly on the emotional throttle but showed he’s not shy about opening it far enough to make the whole hall shake. By the time he capped the evening with the hurtle and swirl of Ravel’s Daphnis et Chloé Suite No. 2, he could have announced a run for the presidency and the audience would have elected him on the spot. (Except for the fact that he’s Canadian.)

Conductors can’t simply order up excellence or instruct an orchestra to execute a scripted version of their ideas. They have to rouse musicians into wanting to please them. Some deploy terror, others flattery, wizardly mysticism, good-natured camaraderie, or a mixture of persuasive strategies. Nézet-Séguin relies on overt joy and an intense physicality. Short but straight backed, with broad shoulders and a broad smile, and equipped with marble arms whose contours are visible through his tailored black shirt, he communicates flexibility and easy control. He also projects the serenity that comes with knowing the score the way a harbor pilot knows the channels and shoals. Over the years, I’ve been impressed with the way he doesn’t just burnish details for the sake of a moment’s delight but instead brings out their relationship to a much vaster arc. Just as fractal patterns repeat at different scales along a coastline, expanding from rivulet to firth to fjord, the ripples in the opening of La Mer build up undulating themes, and then evolve into a grand 20-minute swell. When Nézet-Séguin sends a burst of energy crashing through the surface, it doesn’t sound like an arbitrary spasm of excitement but the revelation of a submerged power that has been there all along.

In January, he led Debussy’s only opera, Pelléas et Mélisande, taking over what had been a specialty item of James Levine’s. Where Levine shrouded it in perfumed miasmas, however, the new boss gave it sinew and bone. Microdoses of clarity can have big effects in scores like this one, in which the subtleties pile up. Here, the opera transformed from a symbolist rite into a more human love story, enacted by the sensitive tenor Paul Appleby and the mezzo-soprano Isabel Leonard.

In May, Nézet-Séguin returned for Poulenc’s Dialogues des Carmélites, and once again he blew away the film of dusty preciousness that clings to the score. The libretto deals with a group of Carmelite nuns in post–Bastille Day France, when piety was tantamount to subversion and the penalty was often death. With its cloistered setting and indistinguishable costumes, the opera can feel hemmed in and static, but Nézet-Séguin was having none of that.

In the first act’s emotional linchpin, the convent’s prioress lies on her deathbed, besieged by awful visions but still desperately trying to protect the women in her care. The soprano Karita Mattila, who sang the role, is a practiced hand at high-impact melodrama, punching syllables and regulating the flow of molten steel through her voice. Here, she was a diva of the stage playing a diva of the spirit, fierce and urgent to the end. Had it been necessary, she could have carried the scene on her own. But it wasn’t.

Nézet-Séguin made sure the orchestra lifted her up on her way to heaven, garlanding her confessions with a celestial shimmer, hammering her regrets with a couple of trembling fortissimos, and boosting her waning authority with jolts of imperious brass.

Dialogues is a story of collective martyrdom, a deeply troubling one. A few weeks after seeing it, I read Patrick Radden Keefe’s Say Nothing, a phenomenal chronicle of Northern Ireland during its bleakest years, and the tale of Bobby Sands and nine fellow prisoners, who starved themselves to death one by one, reminded me of the opera’s finale, in which the nuns slowly queue up for their executions. Poulenc saw the nuns as victims and their killers as beasts, but one group’s uncompromising principle is another’s destructive fanaticism.

The opera is also about the impossibility of barricading oneself off from a world consumed by crisis. There are no walls high enough to keep hostile fervor at bay, no calling sublime enough for others to just leave it alone. Keefe describes a society in which ideological rage permeates every detail of daily life — how children play, where friends drink, even how much former fighters eat. In her 2018 novel Milkman, the Belfast-born author Anna Burns describes a teenage girl who wants nothing more than to vanish into a 19th-century novel but attracts the attention of an older paramilitary officer, and so is hauled into the violent present.

Nézet-Séguin seemed to intuit how a similar set of intrusions and paranoias shaped Poulenc’s music, and he brought out the score’s menace and resistance. In the second act, the aristocrat’s daughter, Blanche de la Force, has entered the convent as a novice, and her uncomprehending brother shows up to try to coax her back out: To France’s firebrands, he points out, a cloister is merely a dissidents’ lair to be ruthlessly flushed out. Groping uncertainly with the convent’s discipline, Blanche is clear-eyed and firm with her brother. “I only ask that you think of me as your companion in battle,” she says. “For we are both going into battle, each in our own way. And mine has its risks and perils, just like yours.”

Leonard sang Blanche with an astonishing mixture of softness and backbone. She has steadily marched toward stardom at the Met, and the affinity between her and Nézet-Séguin is evolving into one of the company’s great artistic partnerships. Her voice is purest vicuña: warm, fine, and naturally colored. She can be slow to shed her poise or let anything mar the perfect weave of sound, but in her Blanche you could sense doubt doing battle with determination, a wild heart beating beneath the habit. Even if you’re not French, a nun, a Catholic, or even much of a believer, it’s easy to empathize with Blanche if you’ve ever felt the need to resist political power or the desire to retreat from the world’s cacophonous scrum.

The opera ends with a paradoxical blend of ceremony and drama, a “Salve Regina” that offers no hope of salvation — not in this world, anyway. In this repetitive sequence of ritualized slaughter, every moment is predicted, enacted, and repeated as the nuns file offstage, where the guillotine falls with a rhythmic thwack. Dialogues is never about just one character or one death but about individuals who don the uniform of one all-encompassing faith and are doomed by another. Nézet-Séguin gave the grim, inexorable parade a gathering intensity as hopes of a last-second rescue ebbed.

The chorus intoned, the harps swirled, the sound thickened. Prayer and march merged into a terrible incantation — and even in its awful finality, the scene intimated a new day for the Met.