A century of opera with the Met; The legacy of fine voices ranges from Enrico Caruso to Luciano Pavarotti, Christine Nilsson to Leontyne Price

As of tomorrow night, the Metropolitan Opera will have been at the center of America's operatic life for 100 years. From the first night on Oct. 22, 1883, with the esteemed Christine Nilsson as Marguerite in Gounod's ''Faust,'' the company inhabiting the Metropolitan Opera House has presented the standard repertoire (as well as a few exceptions) with as many of the best names of the day as possible.

The fame started early. Even by the time Enrico Caruso debuted in 1903 at the house on 39th Street - in its second incarnation, having been gutted by fire in 1892 - the reclame of the house was worldwide. Two Puccini operas were given their world premieres on the old stage - the underappreciated ''La Fanciulla del West'' and ''Trittico.''

By that time, anyone considered important would be asked to sing - and would agree to sing - at the Met. Over the years, most of the legends of operadom have trod its boards: Jussi Bjorling, Rosa Ponselle, Leontyne Price, Lauritz Melchior, Kirsten Flagstad, Ezio Pinza, Joan Sutherland. The list of pivotal names introduced in the new house to date includes Luciano Pavarotti, Placido Domingo, and just this season, Jessye Norman. The conductors include most of the greats - Gustav Mahler, Arturo Toscanini, Fritz Reiner, Leonard Bernstein, George Szell, to mention but the showiest names.

In its early days, artists of this stature arrived for several-month stays, or even for the entire season, which typically was two months shorter than today's late-September-to-mid-April stretch. Nor did they all have starring roles: Important artists often performed in roles that are nowadays relegated to second-string singers.

Throughout the years, however, the company's financial status has been tumultuous. It barely survived the depression years. And during the intensely nationalistic periods of the two world wars, many of its most important overseas artists were barred from its stage. Gone, too, were the days when a handful of the wealthiest patrons could meet the annual budget by writing a check: With the costs of opera escalating and the season expanding, the 39th Street house became increasingly problematical.

By the late '50s, in fact, the company was projecting the necessity of a move to a larger, more cost-efficient house at Lincoln Center. To those who felt the Met was just as much the old house itself as it was the singers in the company, the change in locale could not help being seen as a catastrophe: How, they asked , could a new house communicate the sense of history of a pre-1900 edifice?

But financial problems didn't drop away when the Met moved to its new home at Lincoln Center. For his first season in the new house, Rudolf Bing, then general manager, planned a 10-new-production extravaganza season to inaugurate the new theater and create its own sense of memories. But by this time, scenery had ceased to be a series of painted drops and had become massive set pieces that had to be moved in and out on special wagons or on a huge turntable - all entailing large sums of money. Mr. Bing also faced the threat of a strike that would have scuttled the first season. In the end, he capitulated to all union demands so the curtain could rise on the first night of the Met's new era.

Those costs - both production- and union-related - have continued to haunt the company ever since, through the difficult Schuyler Chapin years and up to the current Anthony Bliss tenure. An example: The Met's current production of ''La Boheme'' is said to have run to more than $750,000.

So serious did the problems become in the mid-1970s that it looked as though the company would go under. At that time, Marilyn Shapiro was brought on as director of development, and financial stability began to be restored.

''I felt, in looking at the universe of donors that were giving in '77,'' she said recently, ''that there was a great potential if we could put together a program that in a very organized way expressed our appreciation to our donors and got them involved behind the scenes.'' Her program included backstage tours, open rehearsals, and ticket-buying privileges - with benefits increasing in proportion to the amount of contribution. It was a huge success: Subscribers and patrons gave generously to ensure the future of the company.

For many observers, the last 10 years have been the most remarkable for the Met. Since the advent of Anthony Bliss as general manager, the house has turned itself mightily around - becoming, at last, a financially sound institution. Not surprisingly, balanced books sometimes seem just as important to the company as artistic triumphs - though Mr. Bliss constantly points out that if the product is deficient on stage, the entire financial plan is for naught. At the core of that plan is a $100 million endowment goal that is now 82 percent pledged. The company staff has expanded considerably - mostly in development, marketing, and other managerial capacities.

These days, the Met has more visibility than ever before. As Marcia Lazer, director of marketing, sees it, ''In the old days, you weren't doing well if you had to advertise - and by not advertising you didn't do too well.'' The goal today, she says, is ''making the institution and the product accessible'' - whether by newspaper ads or nationwide mailings to the entire membership, ''making sure they know they get value for their money.''

But none of this will matter if artistic levels are not of an international standard. Music director James Levine (soon to become artistic director) has raised the caliber of the Met orchestra to exceptional levels. The noted opera conductor Richard Bonynge is not alone in saying it is the best in the world today, night after night, performance after performance. Under David Stivender, the chorus has blossomed anew as an impressive instrument. The level of performances has set a new standard of consistency.

Yet the grand irony of it all is that fewer nights of sheer magic happen these days. Part of the reason is that the company has dropped the old repertory format in favor of the European stagione (literally translated ''season''), implying that one cast stays for the entire season of the production. In the old days, by contrast, productions were planned for the convenience of visiting stars who wanted to do four or five roles during their annual visits.

Most observers feel that the stagione system helps ensure the feeling of an ensemble for the performance - a plan that works splendidly in houses doing only two or three performances a week. But the Met offers seven a week. Artists now have to be willing to spend a long stretch of time, from preliminary rehearsals to final performance, in New York. In Europe, on the other hand, they can fly about, singing between dates and amassing fees. As a result, many observers feel they are less willing to come here and sing. It is rare, in fact, to have a star singing more than one or two roles a year. One good effect: The frequent turnover of stars in various casts no longer happens, helping to guarantee that the horror nights of standby singers bunched together happen less frequently. But the lack of turnover also tends to preclude the sort of casting combinations that often electrified evenings in the past.

Along with casting come matters of repertoire - an area in which Mr. Levine has strong preferences. His attempts to expand the musical boundaries of the company have been received with mixed praise - from the unanimous acclaim for Alban Berg's ''Lulu'' to the financial fiasco that has been Kurt Weill's ''Rise and Fall of the City of Mahagonny.'' (Ironically, ''Mahagonny'' is back this year, ''Lulu'' is not.) Levine has also cultivated his core of favorite singers - although in a few cases he has kept careers alive far beyond their vocal means and has encouraged young singers who may not have been worthy of this institution.

Then, too, there have been those celebrated battles between singers and management - Maria Callas's tiffs with Rudolf Bing and, more recently, Joan Sutherland's with the current administration. But that public volatility barely reflects the private chaos and disorder that had been the state of the Met's planning department for so many years. Observers agree that those days are over: Whereas once artists could be booked only a few months in advance, the company is now committing four and five years ahead to singers and roles.

Many Met-watchers give credit for the change to assistant manager Joan Ingpen. She has put so much order into the chaos of Met schedules that most important artists can know to the minute what they'll be singing and rehearsing four years hence. But she has also come under fire for casting choices that smack more of convenience than of artistic merit.

Throughout the years, however, the Met has sustained a national image - even in the wake of the proliferation of smaller and larger companies around the country. The demand for live telecasts appears to be unabated, and out-of-town donors, who more often than not know the Met through radio (the Saturday afternoon Texaco broadcasts) or television, also tend to support their local opera companies - since, as Miss Shapiro notes, they ''realize there's a relationship between the (standards that the Met sets) and the rest of the world of opera. . . .'' And Jane Hermann, director of presentations, emphasizes that ''If you didn't have those singers under Met contract . . . all these companies would not have the opportunities to get them. We provide a tremendous service to other companies.''

And the Met continues to retain a strong international reputation. Word of mouth among singers has sustained its image as one of the finest opera houses in the world. Heads of European houses tell Met officials what they hear from the singers: that the highest day-to-day standards of opera are at the Met.

But opera, as its buffs readily admit, has always attracted something of a lunatic fringe. People get lost in the experience of operagoing - the mix of sets, costumes, singing, orchestra, the size of the theater. It can be a hard habit to shake. Unfortunately, opera is also mightily expensive to produce - and on the scale the Met produces it, many would say it approaches folly.

But the company manages to survive. During times of artistic unrest, it can appear that it has seen better times. But even if it does not always live up to its ideal as a great opera house at all times, it now has a financial base on which to build for the future.

Where will that future take it? Mr. Bliss wants to see enough of a cushion to allow the company to take chances with new operas. The Met, many critics feel, has the potential to be in the vanguard of opera in the latter part of the 20th century. It now has the chance to make the best possible opera happen on a regular basis.

And at its best, even in this era of shortages in voices, it offers a thrill that few houses in the world today can guarantee - let alone with the regularity the Met boasts when all of its various elements are working together in peak form.