Paella pans are most often made of thin carbon steel to quickly transfer the heat to the ingredients. The most frequent problem with these pans, is rusting from improper storage. This is easily preventable. Treat your pan properly, & it will last for many years of making paella.
Carbon Steel: Before first use, your pan needs a good wash to remove the manufacturer's special anti-rust coating. Do this with hot soapy water. Ideally, heat some water in the pan with a dash of cider vinegar. Simmer for 10 minutes or so & then rinse. Be sure to dry the pan thoroughly, then lightly coat the inside with a little vegetable oil. This seals the surface to prevent rusting. If any rusting does occur, a bit of steel wool will usually remove rust.
When cooking with carbon steel, don’t leave an empty pan over direct heat for more than a few seconds. The metal is thin and could overheat, which will cause a dark splotch in that part of the pan. Since the paella pans are made from a relatively thin one-ply material, they heat up & cool down more quickly than other pans. This is a good thing for making paella, but be aware that you shouldn’t set an empty steel pan over direct heat. If an empty (or nearly empty) pan is left over strong heat for too long, the pan could discolour or warp. But as long as there is broth or food in the pan to absorb the heat, it will be fine. Just remember, this is not a pan that calls for pre-heating to get a good sear.
Enamelled: Don't require any special care or maintenance. Wash them before the first use & you're ready to go. Handle with care as a hard knock against another pan or hard surface could cause the enamel to chip. Generally this is only cosmetic and won't affect performance.