craftgrrl | glue for metal and wood?

So, I know I'm a little late, but I've been working on a project for my boyfriend. I wanted to get it done by V-Day but I've been busy and felt sort of non-creative for awhile. Anyway, I bought this really cute wooden box that I have almost gotten completed. I've painted it inside and out, several different coats. I glued feathers to the inside of the box. In the middle I wanted to glue this old fashioned key I've been holding onto since I was little. But I've tried every kind of glue I own and nothing is sticking. (I even have a glue I used for sticking mirror pieces on a painted canvas and that didn't work either!)... and obviously hot glue doesn't work because of the smooth surface of paint.

Please tell me there's something I can use! Thanks!