Metal frame doors are not always as strong as one might think.  People often place items in between the hinges and wall to prop the door open without knowing it is one of the worst things someone can do to a door.  It puts a tremendous amount of force into the hinge and ends up bending the metal hinge pocket in the door frame.  Which then causes the door to sag, prevents it from closing properly, and might get flagged in a fire inspection.  Unfortunately, in most cases, the damage to the hinge pocket in the metal door frame can not be fixed and the frame will need to be replaced.  To save yourself the cost of installing a new frame and door, you can try a continuous hinge that runs the length of the door.

This is especially common in garbage room doors where dumpsters are being moved around.  Apartment buildings and high rise condo units where people are moving in and out on a somewhat regular basis.