Buddy, for example, has a mostly aluminum frame. That frame has a flat bottom to the top tube, and has the other tubes variously shaped. Buddy's wheels have metallic bladed spokes and a medium deep rim. There's no reason it couldn't have had a very deep rim. In fact, all of this is mild when it comes to shapes that can be made from metal. Ducommun Aerostructures, has several photos of wild looking one-piece metal components.Similarly, Accudyne has different wild photos. Between forming processes, casting, welding and such, any weird and wonderful shape can be made from metal, including some that would not be a good idea with composites.
Lest we harbor any lingering doubts, do not forget that the fastest aircraft (at least that we know of) was made of titanium. Namely, the photo below, from Wikipedia. Now THAT is aero!
A-12 from the Intrepid Museum, from Wikipedia