Elegance has a way of pouring out of Miriam Miller. Her arms open like wings, her fingertips part like petals. At 5 foot 10, with long legs and an elastic back, she has the kind of line that goes on for days.

But a body isn’t everything in ballet. What makes Miller so striking isn’t what you see but what you instinctively feel: her aura. Resolute yet plush, her presence has a quiet command and, within that, an almost casual confidence.

At New York City Ballet, where she was recently promoted to principal dancer, Miller, 28, has that rare ability to dance onstage as if she were singing through the steps in an open meadow. “I don’t love doing ballets that are performative to the audience,” she said. “I like it when it’s more internal, and it’s the audience looking in on you and seeing you approach and explore.”

Over the past couple of years she has become her own dancer — not Miller dancing someone else’s part, but Miller being herself. On Thursday, she makes her debut in the dual role of Odette-Odile in “Swan Lake,” with Chun Wai Chan as her Siegfried. The weight of carrying this ballet, for any dancer, is both a technical and emotional feat. Timing is everything. Miller’s consistency has caught up to her beauty. And she is a swan.