Last night the Metropolitan Opera opened its two-week run in the Kennedy Center with Puccini's "Manon Lescaut" filled with vivid, arresting staging by Gian Carlo Menotti and conducted with constant nuance and gorgeous lyric expression by James Levine. But the singing was uneven and the work as a whole rarely caught fire or captured the attention for very long.

Puccini's "Manon Lescaut" is the first opera in which its creator's real genius openly asserted itself. Its unquestioned strengths and clear weaknesses require unusually sensitive stage direction and powerful conducting if the opera is to hold the attention of audiences. it also needs beautiful singing.

Under Levine's direction, the orchestra played with a beauty of sound that emphasized the richness Puccini first achieved in this score. And David Stivender's notable training of the Met chorus produced distinguished results in the first and third acts, where the requirements are intricate and extensive.

Menotti is, in addition to a creative genius as a composer of opera, one of the world's master stage directors. He has added touches to the Prevost-Puccini story that clarify its principal action and continually enhance with subtle details its subsurface emotions. In the second act, Menotti showed us, with the help of Renata Scotto's skilled acting, all of Manon's brittle exterior as well as her honest feeling for Des Grieux. The nervous fluttering of her fingers said as much about her as her passionate abandon on the bed. How could any tenor resist her as Mauro seemed to? At times Scotto almost seemed to be overacting to compensate for her wooden partner. In the third act, Menotti made the roll call of the girls being deported to the Louisiana colony of scene of touching and varied detail.

The opera centers around the famous Manon of Abbe Prevost, the young girl on her way to a convent who is so easily seduced before reaching it, and who quickly learns to love both her young Des Grieux and the jewels her aged Geronte supplies. Scotto offered an example of the art of making every gesture, every motion of hand or eye or body an illustration of all that Manon was thinking.

The first act of the opera gets off to a slow start, but by the second act, after Manon had dumped Des Grieux and become the pampered darling of her old Geronte, Scotto was in such complete command of the stage that attention was riveted on her. And she rewarded the watchers: clever business with a dropped earring; rushing about to collect all her jewelry before Geronte's return; the agonizing separation from Des Grieux when she was to be deported; and the infinite detail of her death scene. All these were managed with the gifts of an actress who would be great even if she did not sing a note.

Scotto, however, sang a great many notes, some of them exquisite, soft textures, all of them shaped to project the inner meanings of every word. When she reached "In quelle trine morbide," she was in her finest vein, with a consummate wealth of shading. Even when Puccini called for high, open top notes, Scotto held back nothing, though the sound up there turns raw and the vibrato windens unpleasantly.

Among her colleagues Scotto was superbly supported by ideal singing from Pablo Elvira as her brother and Ara Berberian as her old lover. Both men demonstrated the art of fine singing, all the while adding stylish enunciation and polished acting. Ermanno Mauro, singing Des Grieux, lacks the artistic impulse to a distressing degree. There is a crudeness in much of his attack and, opposite a Scotto, his acting looked more than usually primitive. Nothing more fully displayed his lack of taste than his opening of "O tentatrice!" A fine natural voice is not enough.

There were excellent singers in brief roles: Ariel Bybee as the musician, Philip Creech as Edmondo, Richard Vernon's sergeant, and Dana Talley's lamplighter filled out the large tapestry with style.

The set for the last act, and the lighting in acts one, three and four looked little better than dismal. After the Washington Opera's extraordinary "Love of Three Kings," the Met looked rather shabby.