The problem with the metal would be...a fun house mirror effect...really odd images, unless you are very close, and even then...
I think this would work the best for you, you could glue it to wood, or just hang it with whatever, then roll it back up when not in use.
Edit: Just saw this at that site.
"Other uses we have had requests for this product include temporary mirrors for theatrical productions"
So, I'd say that would be a place to start.