I wouldn't use it on the interior of a cage. I suppose you could use it on the exterior. It won't really stand up to the humidity inside a cage very well.
:got a question on a cage I am building as I type... Can I use latex semi-gloss paint on the backside of a cage? It will not be exposed to anything except the wall behind it lol..don't really want to have to use poly. when I can just use left over paint... :And can I use it on the ceiling of a cage for a Green Iguana? will it stand up to the humidity or will I need to seal it? :Thanx! :Roxanne