How to bend back in place bottom of metal door?

Hello. Does the metal piece come off? You could put it in a vice to straightened. Otherwise use a rubber mallet to pound it back. You could also try to use pliers to bend it back. Good Luck!

Sounds like you are saying the steel door skin has pulled away. Sorry, but it's time for a new prehung exterior door, which includes the threshold. Anything you do to it now will have the durability of masking tape.

Do you have a picture of the area you can post? I hate answering questions like this without really seeing what the problem is? Is the area still swelled? Does the door hang up on it now at all when you close the door? Or one of those trip hazards? It could be as simple as taking a rubber mallet or a longer board and a hammer to beat on the threshold. If you can get some adhesive like maybe liquid nail under it might help glue it down? You’ll need to weight it down for several hours if you use liquid nail? Worse cases you may need to drill a hole in the threshold and taper the hole so you can flush mount a screw? Depends on the gap, but you may just need to put some waterproof silicone if the rain ever hits the threshold? Seeing your threshold be a lot easier to come up with better solutions hopefully?