“Bess, you is my woman now,” the disabled beggar and unlikely hero of Gershwin’s “Porgy and Bess” sings when he realizes that, somehow, Bess — desirable, though troubled — may actually love him. She has been a lost soul, a glamorous, hard-drinking woman with a drug addiction who has allowed herself to be claimed by bullying men. Being with Porgy seems to offer a way out, a chance not just for decency, but also emotional stability.

There is no more moving, or consequential, love duet in all of opera. And that’s how it came across on Monday when the Metropolitan Opera opened its season with a splendid new production of “Porgy and Bess.”