One of my caps is stuck on my valve stems. I have metal caps and I think its rusted on the valve. Anyone know an easy way to get it off without damaging the valve and causing air to leak out of the tire?

 

I would try letting it soak in *penetrating* oil for a couple of days, then give a few taps with the end of your pliers, then try to remove the stem. In the absolute worst case, you rip the stem, install your spare, and drive to a tire shop that will give you a new stem for like $5+labor.