Why does my dryer sound like it is rubbing metal to metal when running. It is only a few years old but we do a lot of laundry

It probably is metal yo metal. Depending on the model you have teflon strips that wear down and some models have a ball and socket joint at the back. These wear out. The jooint at the back needs high temp. Grease. If it sounds like metal grinding you need to stop using it now and its not hard to fix. But if you keep running it that way the damage caused will cost more in parts then the dryer is worth.