It works great on metal and seals tons of stuff. Mod Podge can be used on paper (as glue) and most likely plastic. I don't see why not. It dries clear. As you can see in the link below (metal container that I used it on) I coated the entire thing with Mod Podge, including the ribbon, etc. The 2nd link is the bottom of the container. The fibers were pasted down with Mod Podge - I used it as a glue. This stuff is great!!!
The 3rd link I used Mod Podge as a glue to create a Faux Silk card.
Good luck! Can't see what you create with it!!!
Gallery at Splitcoaststampers
Gallery at Splitcoaststampers
Gallery at Splitcoaststampers