Artist Marshall Astor made a functional Rubik's Cube out of bronze. He describes how the Cube is designed and how this complicated a project that would use plastic parts to move metal pieces. Astor also mused philosophical on the project:
In making a Rubik’s Cube with undifferentiated sides, I was attempting to remove the concept of solving or of having a purpose or goal from the Cube. I wanted to create an object that better reflected my own feelings about the Rubik’s Cube, and in a broader sense, about the fundamental nature of the Universe. I view the Universe – or all observable phenomena – to be a purely subjective concept, best defined as the intersecting agreement between all potential subjectivities. The Cube functions as a receiving object, by denuding it of it’s role as a puzzle, it becomes a more intellectually malleable object, and the physical action of operating the Cube has a more personal meaning.
Well, aside from that, what I found most interesting about the article was how the seemingly simple Rubik's Cube is actually a very complex machine that is not easily duplicated in a medium other than plastic. You'll find more pictures and a comprehensive guide to how he made it (including patination with his own urine) at the link.
http://www.marshallastor.com/projects-art-stuff/the-cube/ via GearFuse