The Metro subway, despite its continuing history of precarious financing and political peril, is beginning to make a indelibly positive mark on the economic fabric of the metropolitan area and to change the travel habits of at least some area residents.

The year past has been one of extraordinary achievement for Metro. It has seen the fledgling rail system grown from a weekday commuter railroad confined to the urban core to a full-service transit system reaching as far as the Beltway.

In 1978, Metro opened lines to Silver Spring and New Carrollton and now has almost one-third of its planned 100 miles in operation. To be precise, 30 miles of double-track railroad and 33 stations are serving area passengers.

Accompanying Metro's expansion has been a building boom in downtown Washington, in the Arlington County business areas of Rosslyn, Crystal City and Pentagon City, and in Metro East, the business-industrial park near the New Carrollton station in Prince George's County.

Growth in the Washington area would doubtless have occurred without Metro, but there is no question that Metro is directing some of that growth and encouraging some more of it.

"I thought that Metro was an enormous boondoggle," developer Leonard Abel told the The Washington Post in November, "but now I think that it will be as important to the salvation of the city as the Beltway was to the development of the suburbs."

A number of things are happening to downtown Washington that make a transit system such as Metro's an asset. There is enormous development under way in the West End -- parallel to the Blue Line. New development and redevelopment, including the Convention Center and plans for refurbishing the Pennsylvania Avenue Corridor, promise to return the "old downtown" east of 14th Street NW to the prominence it once held. A number of stations on both the Red and Blue lines are in place to serve that development.

Metro is seeking proposals for a development project on top of the Van Ness -University of the District of Columbia Station, which will be on the Red Line extension from Dupont Circle that is scheduled to open early in 1981. About 65,600 square feet of land and air rights are available.

Every time Metro opens another line, it develops a wider following, as Metro's ebullient spokesman Cody Pfanstiehl often points out. Even in the year of Proposition 13, not one single politician running for local office in the metropolitan Washington area suggested anything other than completion of the system.

It was not always tht way. As recently as 18 months ago regional politicians were openly asking whether Metro should be turncated and the federal government was saying that its support for Metro ended at the 60 miles presently funded or open for operations.

Transportation Secretary Brock Adams has now said that the federal government "supports the goal of completing the 100-mile system," and has placed the ball back in the local court.

With the federal commitment in place, local area governments will either find a way to assure long-term financing for both the construction and operation f teh system, or it will be their fault if the project fails.

Metro is now estimated to cost about $7 billion to complete. The annual operating deficit for the subway and the feeder bus network has been projected to reach $33 million to $500 million annually in escalated dollars by 1990. The variables in the size of that deficit are ridership and the level of fares charged. The present deficit is about $100 million.

Metro collects almost 50 percent of its total bus and subway operating costs in fares, more than the national average. In fact, not one big-city transit system in the United States is presently paying its operating costs from fares. Almost all cities have dedicated, assured outside ta sources to finance their deficit. Metro officials will be seeking authority from the Maryland and Virginia legislatures and the District of Columbia government to secure such sources for this area.

While the search for financial security continues, Metro's ridership grows. The opening in November of the Orange Line to New Carrollton brought Metro ridership to a weekday average of about 220,000, an increase of about 20,000 per day.

Saturday service, which Metro started in September, has attracted as many as 80,006 people (on Dec. 16) and as few as 54,684 (on Dec. 23), but has been averaging well over the 61,000 riders Metro predicted.

Metro General Manager Theodore C. Lutze has proposed inaugurating Sunday service in fiscal 1980, but that proposal has yet to pass muster at the Metro board. Another new feature in Metro operations came with the opening of the Orange Line to New Carrollton; the addition of readily accessible parking spaces. The parking lot at the New Carrollton station itself, located just inside the Beltway at Rte. 50, was full the first day and has been full every weekday since. It has 1,900 spaces.

A large lot at the Landover station has yet to fill, but attendance has been increasing steadily. The same is true at Cheverly. Many of Metro's riders, according to surveys done by the Washington Post, by Metro and by others, would have taken their cars had there been no Metro. It is too early to assess any long-term impact Metro is having on automobile traffic, because the New Carrollton line has only been open two months and it is the first Metro link to reach the Beltway.

Although Metro has another 30 miles of subway line under construction, only 2.9 of them will open in 1979. The Orange Line from Rosslyn to Ballston, near Fairfax Drive and North Glebe Road in Arlington County, is scheduled to open late this year. That will add four stations to the system, all in the somewhat depressed Wilson Boulevard-Fairfax Drive corridor.

In addition to the visible impact Metro is having on development, it is also one of the region's largest employers, with a total of 6,178 employes, two-thirds of them of racial or ethnicminorities.

In 1978, Metro contractors poured 400,000 cubic yards of concrete, bought 16,000 tons of reinforcing steel and used 12 million board feet of lumber.

Woodward and Lothrop, which is renovating its main downtown store to take advantage of direct access to the Metro Center station, told Metro officials that their bassment fast-food joint sold 126 pizzas and 25 inches of hero sandwiches on Sept. 9, a Saturday when Metro was not open.

On Sept. 30, the day Metro started Saturday operations, Woodies sold 245 pizzas and 102 inches of hero sandwiches.