DAVID SMITH, the sculptor, was a herculean hero. He seems a creature from a legend, Paul Bunyan-big, John Henry-hard. In the still unfolding history of modern metal sculpture, no master looms as large.

Blacksmiths were his teachers. He earned his daily bread building tanks and locomotives, "laying down 120 feet of weld a day." He died, as Casey Jones had died, in a crash of steel. The art he inspired has not fulfilled its promise -- a thousand lesser hacks and ten thousand lesser sculptures by junk collectors, tinkers, and Cor-Ten academics have nibbled at its beauty -- but Smith seems gigantic still.

His secret is this: The sculptures he left us, despite their found and abstract elements, are not merely sculptures. They are statues, too.

His imitators decorate. But David Smith fought battles. He performed mighty labors and wrestled mighty foes.

He wrestled with Picasso first, his exemplar and his enemy, and later with the guilts and rages that seethed within his psyche, and battled on until, in the last years of his life, he reached a kind of calm, a sort of shining balance, that let his art confront the landscape and the sky. He worked steel plates as easily as other men work wood. And late in life he took the two divergent strains of European modernism, the Cubist and the Surrealist, and somehow welded them together. From Freud and the Surrealists, Smith had learned to dredge his own unconscious. And in European Cubism, he had found a means of using semiabstract signs -- emblems, gestures, hints -- that let his viewers reinvent the way they sensed the figure. More than any other sculptor of his time, Smith took these two opposing strains, and somehow made them one.

Three Smith exhibitions are now on view in Washington. Two are at the Hirshhorn Museum and Sculpture Garden. One of these, organized by the Archives of American Art, is full of documents and sketch books and photographs of Smith at work. The other, "David Smith: Painter, Sculptor, Draftsman," organized by the Hirshhorn's Miranda McClintic, includes 163 unfamiliar works, some of them amazing, many raw and ugly, that together trace the complex path he followed on his climb. The third Smith exhibition, and the most imposing, opens Sunday at the National Gallery of Art.

"David Smith," organized by E.A. Carmean Jr., excludes the sculptor's gropings, his failures, his experiments, and concentrates instead on the seven major series -- the Agricolas, the Sentinels, the Zigs, the Circles, the Voltri-Boltons, the Wagons and the Cubis -- which absorbed the artist's energies in the last years of his life.

The documents and photographs of the Archives' exhibition let us hear his voice and let us see the man, his Bolton Landing, N.Y., studio, his big and bear-shaped body, his huge hands and arms, his hoists and chains and torches, and the clumsy metal caps of his heavy workman's shoes, but these are merely footnotes. McClintic's exhibition, perhaps because it does not try, fails to discriminate between Smith's triumphs and failures.

The Hirshhorn exhibitions seem, at least in memory, to function as appendices to the less-than-perfect show at the National Gallery. Smith's art is not at peace there. Smith, who dreaded selling them, knew that his late sculptures would never look as grand as they did at his "sculpture farm," planted there together, outdoors in the snow, or in the changing sunlight of the rolling, tree-fringed fields of his Bolton Landing home. Here they somehow seem attacked by the shadows, ramps and bridges of I.M. Pei's East Building. Yet these shows, seen together, provide an awesome portrait of an awesome man.

He was endlessly ambitious. He worked 12 hours every day. Early on, he somehow sensed he would one day achieve greatness. He seems to have saved every scrap, every sketchbook, every note and awkward painting, and every obscene doodle, as if to show posterity the pit from which he'd climbed. For the first half of McClintic's show, Smith seems to be obsessed with the genius of Picasso, yet he refused to meet him, lest he had to call him "master."

Something in his character welcomed contradiction. He saw beauty in raw steel, and in violence, too. Smith devoured everything, the high art of museums, the noise and dirt of metal shops (he first learned to weld in a Studebaker plant), happy dreams and nightmares, angry '30s politics and Kenneth Noland's targets. He felt rage at mature women and love for his young daughters. Smith, at Bolton Landing, dreamed of clanking cities, and while in the city yearned for country peace.

He pushed sculpture toward abstraction, but would not jettison the past. Carmean contends that "Agricola I" may have been inspired by the "Mercury" who tiptoes on the fountain in the Gallery's rotunda. Smith's "Lonesome Man," a little silver sculpture in McClintic's exhibition, suggests the gliding reverie of Gilbert Stuart's "Skater." Smith said that Indian temples led him to use wheels in his Voltris and his Wagons.

His first painting at the Hirshhorn, dated 1930, includes the same suggestive forms, the disc, the jutting angle, that appear in his Circles. He confronted in his sculpture all the art of Europe--and all that he recalled of his native Indiana. In his Sentinels and Cubis one sees how much he learned from Picasso and Gonzalez and old Mediterranean art, but in them one sees, too, how loyal he remained to the monumental presences, the heavy-wheeled cannons and uniformed bronze statues, of Midwestern village greens.

He moved from painting into sculpture, until by grinding stainless steel, he made the shining surfaces of heavy metal sculptures suggest spaces as light-filled and immaterial as those of any abstract painting. His Sentinels stand guard. His shining Cubis stride and reach up to the sky. Almost all his sculptures manage to suggest both flesh and welded metal, both aftersight and foresight, advances and returns. Smith did not draw or paint particularly well. His art, though always bold, was not at first original. But he never ceased his striving.

In 1962, three years before he died in a car crash, Smith put it all together, producing 27 monumental sculptures in only 30 days--in an abandoned steel plant in Voltri, Italy. Impressive as his Voltris are (they were shown in the East Building in its inaugural exhibit), his dreams were even grander.

"A dream is a dream never lost," wrote Smith. "I found an old flatcar, asked for, and was given it. Had I used the flatcar for a base and made a sculpture on the top, the dream would have been closer.

"I could have loaded the flatcar with vertical sheets, inclined planes, uprights . . .

"I could have made a car with the nude bodies of machines, undressed of their details and teeth --

"I could have made a flatcar with a hundred anvils . . .

"In a year I could have made a train."

His ambitions knew no limits. He achieved them in a way. Even at its purest, his art is somehow freighted. His last works carry with them the record of his life. Smith collected rusting junk, old decaying rages, enmities, affections, and synthesized out of the mess a clean and complex whole.

His National Gallery exhibit, funded partly by the American Medical Association, closes April 24. His Hirshhorn shows will run through Jan. 2.