Seymour Lipton's metal sculptures have about them something timeless -- and something dated too.

They seem possessed by spirits Biblical and mythical, they suggest prophets and archangels, birds of prey and birds of peace, seafarers and poets. The warriors we meet in them wear armor, hoods and cowls.

Yet these sheet-metal objects, with their heavy masses, their voids and forceful thrustings, also bring to mind the '50s of the New York School and befinned Detroit cars.

When the images these works evoke -- of heroes from the Bible and shiny porthole Buicks -- clunk against each other, Lipton's ageless universals begin to seem portentous and his jutting, curving '50s forms seem yet more out of date.

"Seymour Lipton: Aspects of Sculpture," the thoughtful exhibition that goes on view today at the National Collection of Fine Arts, does not stress the symbols or the confident-yet-anguished spirit of his sculptures. It is instead a show about how they came to be.

David Smith is dead. So are Gorky, Gottleib and Rothko, but Lipton is a survivor. Like them he filled his early abstract art with hints of myths and ghosts. He is, at 75, one of our last links with post-war New York art.

He was born in that city, trained at CCNY and later at Columbia. In 1927 he became a dentist. Though even as he made his living from teeth and gums, he worked daily on his art.

He hung out on 8th Street with Reinhardt, Kline, De Kooning, and other now-famous painters of the day. The artists of "The Club" would talk half the night of FDR and the unconscious, of Jung and the Depression, of society's injustices and of myths and dreams.

The artists of the New York School, so we have been told, believed in sudden action and thought spontaneity a virtue. But as Harry Rand, the National Collection's curator who organized this show, points out in his catalogue, the art of the abstract expressionists, despite its "automatic" gestures -- thrusts and drips and splashes -- is not as impulsive as it might appear.

The color paintings of Franz Kline, now hanging at the Phillips, were not made spontaneously. Kline worked from small studies and planned his sudden, violent brushstrokes with great care.

Lipton in his own way is similarly patient. His monumental sculptures grew from tiny studies, drawings and models. His step-by-step approach and careful working method are the subject of this show.

The 19th-century sculptors who filled our parks with statues usually began with clay or plaster models that were later cast in bronze. Many 20th-century sculptors dispensed with such preliminaries. David Smith, Julio Gonzalez, Alexander Calder and, of course, Picasso, worked directly in hard metal. Seymour Lipton's method is somewhere in between. Though his full-size works evolve from small 3-D sketches and table-size maquettes, his models -- like his finished works -- are made of tough sheet metal, not paper, plaster or clay.

It is in his maquettes that we see his thoughts evolving. They were not made for display, but there are dozens in this show.

The sculpture he calls "Sailing," for example, is shown here with the drawings and the maquette out of which it grew.

The model shows his method. Lipton at one time cut a round hole in the foresail, a void he later filled. The sail aft was altered, too, as was the jutting prow and the hollow-headed figure who seems to be reclining as he sails the sea. We might admire "Sailing" for the rightness of its forms, but that small maquette, with its adjustments and corrections, its folds and cuts and gleaming dots of spot-brazing, has a special, unaffected beauty of its own.

His finished works are made of sheets of "Monel" metal, a bronze alloy he coats with melted nickel-silver rods.

There is in Lipton's art, despite its inventiveness, something slightly ponderous. It never has looked better than it appears here. The drawings and maquettes lend this exhibition a mood of soaring freedom, and the splendid installation, designed by Val Lewton, gives it legibility and liveliness.