A fight was brewing recently at the Metropolitan Opera, and Angela Gheorghiu was in the thick of it.She and some other singers were rehearsing the second act of Puccini’s “Tosca,” and the moment had arrived when Cavaradossi, the passionate tenor lead, scuffles with the henchmen who are restraining him.Gheorghiu — the glamorous, veteran Romanian soprano singing the opera’s title role in two performances, on Saturday afternoon and Wednesday evening — was standing in such a way that the melee was driving right toward her. Sarah Ina Meyers, the revival’s director, began to pause to give her a new position out of the fray, but Gheorghiu practically shouted at everyone to keep going; she would figure out where to move on the fly.“I will respond; I’m quick!” she told them in an excited, heavily accented tumble of words. “Go, go! Action, action!”“Generally my colleagues say, ‘Angela, relax!’” she said in an interview later. “But I cannot relax. Even when I study at home, I’m there. When I open a score, I’m there. My skin, my cells, they’re all there. I’m alive; I have the fire on me.”Where Gheorghiu, 57, has not been of late is the Met. Though she was long a frequent presence with the company after her debut in 1993, these performances of “Tosca” are her first appearances on its stage in eight years.“It’s an unfair gap,” she said of her time away. “It’s unfair because I know I have my public here, and it’s part of my life.”Grand of manner and demanding, but also generous and gregarious, taking grinning selfies for Instagram with everyone in the room, Gheorghiu is well known — and generally well liked, even by colleagues she exasperates — for being one of the few remaining divas in the larger-than-life, old-school mold of Geraldine Farrar, Maria Callas and Jessye Norman.Gheorghiu’s former manager described her as “always interesting, no matter what — onstage, offstage.”Lanna Apisukh for The New York TimesOld-school in the tumult that has tended to accompany her: cancellations, firings, willful behavior, a long marriage of ups and downs to the star tenor Roberto Alagna (until their divorce 10 years ago). And old-school in her voice, which as she was gaining renown was full and dark-hued, flexible and free to the top of its range.“She is a serious artist,” said Jack Mastroianni, who spent years as her manager. “I think sometimes people forget that because of the sensational news that comes out of her cancellations, or whatever. She’s always interesting, no matter what — onstage, offstage.”Because Gheorghiu was joining a “Tosca” run already in progress, she wouldn’t be getting any rehearsal time onstage, with the orchestra, or in costume.“I don’t know what was on his mind,” she said of Peter Gelb, the Met’s general manager. “First of all, he offered me one performance. And I said, for one performance, I will not come. Just one? Come on. I would spend it all on my flight! And of course I need a hotel. So, two.”But why accept a mere two?“Because,” she said, with a sigh, “I must tell you the truth. I adore this city. I adore this theater, from the very beginning.”At the beginning, it was a love affair. Of Gheorghiu’s 1993 debut, in “La Bohème,” Alex Ross wrote in The New York Times that “the preternatural beauty of the voice made a lingering impression.”Ovations at the Met were a long way from small-town Adjud, Romania, where she was born in 1965 to a dressmaker mother and a train operator father. The Soviet-backed regime of Nicolae Ceausescu was then just beginning, an era that later informed her depiction in “Tosca” of life in early-19th-century Rome amid the repressive forces of the police chief Scarpia.“Tosca, it’s myself,” Gheorghiu said. “I’m an opera singer, like her. And I’m not a killer, but I lived in a situation in Romania where you had no right to say something, where you were all the time afraid.”From left, Gheorghiu, Plácido Domingo and Waltraud Meier in “Carmen” at the Met in 1996.Sara KrulwichAs a child, she was obsessed with Leonard Bernstein’s television specials, and began to study voice seriously in her early teens.“I was an opera singer, all my life, from the beginning,” she said. “It was so clear. I didn’t have a Plan B. Never, never. And for all my roles, from when I was 18, I had no teacher, no coach, no pianist. I am my own everything.”Mastroianni said: “What she went through to get from where she was, it takes guts and moxie. And she has that in spades.”Gelb first heard her sing Violetta in Verdi’s “La Traviata” in the early 1990s, then tried (unsuccessfully) to sign her to Sony Classical when he ran the label.“When she was singing ‘Traviata’ in her prime,” he said, “I think hers was the greatest ‘Traviata’ of that time. She was a throwback to the kind of glamorous divas of previous generations, with incredible artistic personality and charisma.”Her voice — clean and pure, with alluring depths but without heavy vibrato or overwhelming size — was perfect for capture on CDs. It was the tail end of the classical recording industry’s heyday, and she was lavishly promoted.“It was a voice that microphones loved,” Gelb said. Gheorghiu still comes across as valuing recordings more urgently than do some singers — “We have to leave a testimony,” she said — and there are certain roles she has sung for albums but never onstage, like an exquisite Cio-Cio-San in “Madama Butterfly.”Almost as soon as she entered the international scene, she became a star at the Royal Opera House in London, a home base in those early years. She divorced her first husband and married Alagna; in a curtain speech before they appeared together in “La Bohème” at the Met in 1996, Joseph Volpe, then the company’s general manager, announced that the two had been wed the previous day. Rudolph W. Giuliani, the mayor of New York at the time and an opera aficionado, officiated.The following year, on tour with the Met in Japan, Gheorghiu refused to wear the blonde wig for her character, Micaëla, in “Carmen,” and Volpe uttered what became an immortal line among opera fans: “The wig goes on, with or without you.” (For one performance, she chose without, and an understudy replaced her.)Appearing and recording frequently as a duo, she and Alagna grew notorious for their hubristic demands. They attempted to veto Franco Zeffirelli’s designs for a new Met “Traviata” in the late 1990s; the show went on, without them. Gheorghiu still sang in New York, but from 2003 to 2005 she was absent for two seasons in a row, which hadn’t happened since her debut.“I feel home here,” Gheorghiu said of the Met.Lanna Apisukh for The New York TimesWhen Gelb took over, in 2006, he tried to rectify this and bring her back in full force. Gheorghiu said that he eventually offered a contract that required her to sing at least 18 performances a year, which would have restricted her ability to take on engagements in Europe.“And finally, I said no,” she said. “And from this moment, I think he was upset. That’s why I was more rare here.”(“I have no recollection of that,” Gelb said. “If I spent my life being offended by opera singers, I would have ended my career a long time ago.”)She abandoned a new Met production of “Carmen,” in which she was to sing the title role, as well as a new staging of “Faust” whose updated concept she disliked.A new production of Puccini’s “La Rondine,” a rarity for whose wistful mood Gheorghiu was well suited, did go forward, in 2009. But over the following decade, there were just a pair of “Bohème” performances in 2014 and the brief stint in “Tosca” in 2015 — in which her voice, never huge, sometimes seemed perilously slender.“When she was last here, there were mixed results,” Gelb said. “Like many members of the audience, she did not like the Luc Bondy production, and she decided to do her own staging. So she kind of defied the directorial team; she sort of went off the reservation.”The current Met “Tosca,” a throwback to Zeffirelli-style realistic splendor, is more to Gheorghiu’s taste, but she is just as headstrong as ever about taking direction. There was, throughout the recent rehearsal, the sense that she wanted to leave as much of the blocking as possible to what her impulse might end up being in the moment.“I like acting,” she said as Meyers, the director, tried, to little avail, to guide her toward setting in stone a sequence in which Scarpia mauls Tosca onto a divan. “But so you don’t see the acting. Reality.”Gheorghiu would like for this not to be her Met farewell; she’d love to sing Fedora here, and Adriana Lecouvreur.“I feel home here,” she said. “I really adore each centimeter: the dust, the smell, the sweating onstage, the costumes, the atmosphere in rehearsal. So I had some friendly discussion with Peter, and I feel like, of course, give me this, then what else? Let’s see how this goes.”Gelb didn’t commit. “But I’ve always admired her and I always will admire her,” he said. “She’s part of opera history, and part of opera history at the Met.” More