Another good trick:
While AC3D doesn't store material presets, it does leave the materials from the previous file in your palette when you create a new file.
If you want to make your own presets file, just create a scene with a bunch of spheres in it with the materials you want to save, then add it to your library. When you want to recall the materials, just load the file up and this will add the materials to palette. Even after you delete the spheres, the materials will stay in your palette for you to apply to other shapes.
These look better textured, but here's one of my metallic base color files to get you started:
http://download.tenfootpolesoftware..../metallics.zip
There's a limit to how "metallic" you can get without environment mapping or raytacing, but as far as simple materials go if you adjust the specular so that it's a little hotter than the base color you can get pretty decent results.