What can I make my cage sides of?

Hello,
Recently I'm making with my grandpa some cages, including big breeding cage and some smaller for catterpillars.
What can I make their sides of? Cloth? Metal? Plastic?
Frames of the cages are made of wood. I've seen on most of photos that are published there that the sides are made of metal.
Could You give me some advices and if you have, photos?
I'll be very grateful