Nintendo recently released a silver version of the DS Lite in Japan, but it still really looks more like plastic than metal to me. If you really want your DS to look like metal how about some real chrome?
The Shock! Magnum Chrome replacement shell gives your DS Lite gaming system a shiny metallic finish. By using copper-nickel-chrome electroplating, the exterior of the case really looks like metal, and is supposed to resist scratches too (although fingerprints are a different story.)
The chrome outer shell is available from ConsoleShop for $39.95 and can be replaced in about 10 or 15 minutes if you have the right tools and follow the directions properly. If you really want to complete the effect, the makers of the case offer a variety of color interior replacements (like the matte black one pictured above) which cost another $29.95 and add quite a bit of complexity to the delicate operation.