wrote...

The head of the screw was facing the floor...the bottom part of the
screw is still in the metal leg.

How can I remove it?

Theres no way (that I can think of) to get to the screw to remove it.

You can buy a screw extractor from an auto parts store. It involves drilling a
small hole in the remaining shaft of the screw, then screwing the
left-hand-threaded extractor into the hole. Works well if the screw is not
corroded in place.