Yes, some pans like Revere Ware have copper bottoms with stainless steel tops. Those and the ones that are all copper are no-no's. Stick to a good stainless steel with a flat bottom and you should be ok. Some older pans will become oval shaped on the bottom after alot of use. Those need to be retired. The pan must set flat, or you risk the possibility of cracking the glass top. The burner needs to have constant conduit to heat, so don't ever remove a pan without turning off the burner. That'll cause breakage as well.