I just had a new door and frame installed today. It looks great, except
I am not sure if the door sill (threshold or whatever it is called) is
done right.

It is the metal part that one walks on, or over, when entering the
foyer. It is a bit flexible when one stands on it, and my old sill was
very stable.

Do I need to call the guy back to put some type of support underneath
it? If I don't, could a heavy person standing on it dent it?

Thank you!

Kate