While performing at Coachella, earlier this month, the singer-songwriter Billie Eilish forgot the words to her song “All Good Girls Go to Hell.” Eilish, who is only seventeen, didn’t seem especially bothered by the lapse. She exuded a cool girl’s sprezzatura, style as nonchalance. Mumbling a little, Eilish wheeled around the stage, like a spinning top about to give out, and then hiked up her shorts, which, baggy and long, were messing with her torque. “Fuck,” she said, turning her back and her mood-ring-gray hair to the audience, “What the fuck are the words, though?” The mistake was so charming that it did not seem like a mistake at all. The audience yelped and the Internet squealed. “I love this,” one YouTube commenter said, below a clip of the performance. “She made it sound like it should have been a part of the song.”

Such reactions are the product of more than your average fan worship. I watch the clip of Eilish and feel a strange reassurance. If the teen idols of the nineties or two-thousands had cursed during a performance, they would have been excommunicated by the pop powers that be. Pop stardom, at the turn of the millennium, was an aggressively packaged and censorious business, necessarily hostile to the unplanned and instinctive, to the performance of anything like whimsy. The teens we revered moved in militaristic phalanxes, and, though they were forced to dress and live as virginal sex kittens, they seemed like robots programmed never to act out.

With her album “When We All Fall Asleep, Where Do We Go?,” which came out in March, Eilish became the first artist born in the two-thousands to rank No. 1 on the Billboard Hot 100. As its ruminative title suggests, the record is about teen angst, leavened by Eilish’s humor and by her fluency in ironic Internet shorthands. The album opens with “!!!!!!!,” a fourteen-second clip of Eilish giggling with her producing partner and elder brother, Finneas, as they make an announcement: “I have taken out my Invisalign, and this is the album.” Later, on “Bury a Friend,” Eilish samples the rough music of a dental drill used during her actual orthodontist appointment; Eilish has described the song as being written from the perspective of a monster hiding underneath the bed. In the music video, the whites of Eilish’s eyes are blacked out. In a sequence in a rubber room, her back is stabbed with syringes. Often, the darkness feels like satire: the song “My Strange Addiction” (“My doctors can’t explain / My symptoms or my pain”) takes its title from a TLC reality show and samples a scene from “The Office.”

Billie Eilish Pirate Baird O’Connell was born in Highland Park, Los Angeles, “three months after 9/11,” according to a profile of the singer in The Fader. She and Finneas, who is four years her senior, were homeschooled by their parents, who are both working actors. Eilish started writing music when she was eleven. Her freakish precocity recalls that of Taylor Swift, who was a strong enough songwriter to sign a record deal at fourteen. But Eilish has a husky, slurring voice that she can thin out to reedy. In subject and in tone she’s more like Regina Spektor or the godmother of West Coast weariness, Lana Del Rey (with whom she has in common a dalliance with hip-hop). Growing up, Eilish watched the film “Spice World” obsessively, not realizing that the girl group in the movie was real. She struggled with feelings of social inadequacy. “My 11-year-old brain was so sad and I didn’t know how to deal with it,” she told Billboard. She has a cinematic, out-of-body approach to songwriting; Eilish imagines herself as a sneaky jinn or a bored wallflower and then writes what she sees.

Finneas and Eilish have developed an anti-Svengali relationship; the two collaborate on a single, shared persona. In 2015, when she was thirteen, Eilish posted her breakout song, “Ocean Eyes,” to Soundcloud. The song had been written by her brother for his band, but Eilish convincingly translated the maudlin dreaminess of lyrics like “Burning cities and napalm skies / fifteen flares inside those ocean eyes.” The track blew up. Today, she has an enormous following among smart and jaded teen-age girls; in January, her music reached a billion streams on Spotify. Her skittish shuffle-step and spooky melodies are now getting radio play, too, but she remains an Internet phenomenon.

Eilish’s expression droops, and her eyes tilt upward like those of a possessed doll. Her quasi-goth style and horrorcore videos have prompted some critics to warn parents to “beware the pop princesses romanticizing death.” I’d argue that Eilish’s creepy confrontations of loss, fear, uncertainty, and death are just what younger listeners need. A generation that was born into a war and is accustomed to having videos of massacres autoplay on their devices should have limited patience for prefab bubblegum pop.

Eilish provides a covertly girlish perspective on the current male-dominated wave of moody, and pessimistic, “sad pop” music. But she has resisted gendered marketing of her music, and her songs mock teen-girl affectations even as some of them are about pining after a boy. She starts off the track “You Should See Me in a Crown” using a sexy baby voice, which dissolves into a sound that is pleasingly sinister. Like Lorde, the young gadfly she most resembles, Eilish has a severity to her. She sings to those of her generation who have grown exhausted by pill-popping numbness—on the song “Xanny,” she observes, “They just keep doing nothing / Too intoxicated to be scared”—and posits that what is actually seditious is to feel.

Eilish aspires to be “genreless,” a byword among young musicians who think that boundaries are passe. “I don’t want to be in the pop world,” she told the Times reporter Joe Coscarelli, over Facetime, in the “Diary of a Song” video series. Too late. The throne for a Gen Z pop royal is open and available. But if Eilish is the future of pop, as some have predicted, it is because pop is a changed sector, one that is ready to abandon materialist concerns and attend to existential ones.