What can I build a sculpture out of?

For science class we have to build a sculpture of an element. I chose copper and decided to make a statue of liberty. I’m planning on having it about 1— 1½ feet tall. I can’t use clay or styrofoam to make it and using coat hangers wrapped in yarn seems to complicated. It can’t be made from food like butter. Lastly the materials can’t cost much. It seems like every material I think of there is some reason why I can’t use.