@cincyjem,
I've seen cabinet hardware that holds the door or lid closed with small installable magnets. In fact, I use a pair of them on the screen door to keep the cats from opening it at their convenience. In a metal door, installation will probably involved drilling and threading holes instead of just driving the screws into wood. Like me, you will probably need a pair of them.
Nothing else comes to mind, but I'm sure there are other ways.