What's your definition of light-medium metal?
I don't recall them costing that much, but yes indeed one would work. They are successfully used in homemade planishing hammers - free plans on the web somewhere, been awhile since I looked.An air powered chisel might. Like a $30 or $40 one from Horror Freight might have on sale. It takes a fair bit of air to run one though.
Not sure what you are trying to do. I don't think a hammer drill will work for shaping metal. I use ball peen hammers and and anvil to shape all kinds of metal. There are many kinds of auto body tools available as well dollies and hammershttps://www.harborfreight.com/automotive/auto-body-trim/auto-body/body-and-fender-set-7-pc-63259.html. I also use a press at times to form different shapes too. There are many types of tools available depending on what you are trying to do. I have an Snap on air chisel that I use on occasion that may be what you are looking for here is one at harbor freight. https://www.harborfreight.com/medium-barrel-air-impact-hammer-61244.html?_br_psugg_q=air+hammer