I have thought about that... the only problem occuring to me is on how do i stick the edges together... should i just epoxy and sand (the epoxy) and colour the epoxy silver?
heres a drawing to help you visualize what i was saying.
oops, sean beat me to it. well, his is a different approach, but the same methods are used.
as far as attachment, just make tabs. along the outer edges of the entire thing, just leave extra metal to make tabs out of. dont cut the tabs off, and fold them inside of your piece. then the tabs can just be glued or riveted to the pieces they touch.
tabs. leave extra metal on half of the outer edges. then just glue the tabs to the backside of the other half of the outer edges
in my drawing, you would put tabs on the outer edges of the pieces that i added to it. then when you fold, just glue those tabs to the backside of the two big "wings"
It's grey or dark black. but mostly you should look for Epoxy thats for metal.
Sold in most hardware stores here in the US as PC-7, Milliput, QuickSteel ect. epoxy... a two part thick paste thats stronger that steel when hardened. It comes in paste form or stick... cut a piece of the stick, mix it by hand and you can apply it like clay. Then sand it smooth.
Google 'Epoxy Putty and you'll find MANY manufacturers if you can't find it at a hardware store near you.