Sheet metal might not seem the most intriguing medium, but it has been an integral part of some of the most exciting buildings in the United States. Starting today, the National Building Museum will allow the public into its cavernous hall for special "Work in Progress" tours of the installation of its upcoming exhibit, "Sheet Metal Craftsmanship: Progress in Building." Workers will labor 24 hours a day to complete the exhibit, set to open Jan. 25.

The exhibit is likely to surprise those who don't usually think of art when thinking of metal. One-third of the awesome space in the Great Hall, which is as big as a football field and 15 stories high, will be filled with a colossal structure -- a free-standing series of towered sheet metal forms -- housing a large-scale exhibit on the history of sheet metal. The sculpture, designed by California superarchitect Frank Gehry, will be 65 feet high, sheathed in steel with brass accents. There will also be a wedge-shaped building with a cruciform tower and two 20-foot-high benchlike forms.

Habitat

With the cold weather, the problem of housing for the homeless is front and center in the news -- and on the streets. Habitat for Humanity has been trying to do something about it for a decade and is now being honored for it. The Georgia-based nonprofit group, which builds homes for the homeless, has received the American Institute of Architects' Whitney M. Young Jr. Citation. It is given to those who use the architectural profession to solve contemporary social problems.

Habitat has taken up that gauntlet with gusto. The unique organization helps people buy and renovate dilapidated housing, with occupants required to work alongside volunteers. It has 239 projects in the United States, three in Canada and 52 in other parts of the world, and hopes to construct an ambitious 2,000 homes in 1988.

NGA News

The National Gallery of Art has added a complementary show to "An American Sampler: Folk Art at the Shelburne Museum." "Naive Visions: Antique Toys From the Shelburne Museum," though April 14, consists of playthings from the 18th, 19th and 20th centuries. Many of the toys are unique handmade objects (though mass production did begin as early as the 1840s, when toy makers began to sell millions of tin and cast iron toys).

And the exhibit "A Century of Modern Sculpture: The Patsy and Raymond Nasher Collection," now scattered around the public spaces at the National Gallery, has been extended through Feb. 15. The show, which has handsomely accentuated the stark East Building, has 74 works by 37 artists, and has been seen by an estimated 1 million visitors since it opened at the end of June. Two more works have been added with the extension: the marble portrait "Hieratic Head of Ezra Pound" (1914) by Henri Gaudier-Brzeska and David Smith's cast bronze "Perfidious Albion" (1945-46).

Theater Art

At the Source Theatre, the art of set design is being used to great effect in unifying the play "Safe Sex," making its Washington premiere at the Warehouse Rep this week. Written by Harvey Fierstein, who has produced other shows with gay-related themes such as "Torch Song Trilogy" and "La Cage Aux Folles," "Safe Sex" examines the effects of AIDS on relationships in both the straight and gay worlds.

"Safe Sex" is split into three one-acts. The first, "Manny and Jake," is about first meetings; the second, "Safe Sex," covers long-term relationships; and the third, "On Tidy Endings," depicts the survivors after an AIDS death. The Source production uses a single set design -- with a graveyard concept -- to tie them together. It looks like an attic of spent human lives -- old knickknacks and curios all cast in bronze. "The set is really a monument or work of art for people who are tragically gone," says the Source's Pat Sheehy.

Dupont Monument

And a real monument for victims of AIDS is in the planning stages. The proceeds from "Metamorphosis," a multimedia collaborative performance Friday and Saturday in honor of the late Jack Guidone, will go to a fund to install a statue in the Dupont Circle area to commemorate AIDS victims. The benefit for Guidone, a local performance artist who died last year, will include dance performances by groups such as the D.C. Contemporary Dance Theater, music by D.C. Cabaret, drama by T.J. Edwards and more.