At Chicago’s, art exhibits, viewers will see metallic frames and wooden frames. Each of these frame types has its advantages and disadvantages. Advantages and disadvantages include aesthetics, construction, display and maintenance.
Wooden frames give the artwork that they enclose a traditional appeal. These frames are suitable for paintings in these styles: Abstract Expressionism, Baroque, Classical, Dadaism, Expressionism, Fauvism, Gothic, Impressionism, Naturalism, Neoclassicism, Neoimpressionism, Realism, Rococo, Romanticism and Symbolism. Most, if not all, Futurism paintings will appear in wooden frames. (Umberto Boccioni’s Unique Forms of Continuity in Space will exhibit itself outside of a wooden frame because it is a sculpture.) I would be surprised if The Art Institute of Chicago displayed most of its paintings in other than wooden frames. Etchings, lithographs and woodcuts are also likely to appear in wooden frames.
Metallic frames give the artwork that they enclose a modern appeal. Viewers are likely to see Modernism, Pop Art and Precisionism styles in metallic frames, especially if they are photographs. (I have never seen an acrylic or oil painting in a metallic frame, have you?)
Metallic frames are easier to cut to custom sizes than wooden frames are. For art exhibits, artists must use the best quality metal and wood. This means that the aluminum metal will be cheaper than the wood (probably mahogany).
Artists can varnish wooden frames, but it would be tacky (and probably unacceptable to art galleries) for artists to paint or varnish metallic frames. It is easier to remove dust and stains from metal than it is to remove from wood. (However, some stains on wooden frames are intentional.)
Placing paintings inside wooden frames is a delicate procedure that involves stretching the canvas. Placing photographs in wooden frames is somewhat easier, involving attaching staples and/or small nails, cutting cardboard mat boards (These boards frame the photos.), and cutting the backing (cardboard or foam) to hold the photos in place. Paintings rarely have glass on their fronts, but photographs always have glass on their fronts.
Large artwork appeals to viewers more than small artwork. However, large, wooden framed paintings will be difficult to hang securely because of their weights. A photograph that has the same size as the large painting, but in a metallic frame, will be easier to hang because of its lighter weight. (The canvas and paint in an acrylic or oil painting has greater weight than the images the photographer has imprinted on photo paper.)
Whether you are using metallic or wood frames, it is usually better to let the experts cut your frames and mat boards. The Chicago Yellowbook lists many framing shops. Michaels, an arts and crafts chain that does custom framing, has 13 stores in the Chicago-land area.