Does anyone have any idea what would cause the doors to rattle on a 99 XLT Supercab?

Both the front doors and back doors have developed major rattling as the truck goes over normal bumps in the road. This first appeared on the passenger side, then on driver side also. From the inside, the doors feel firmly closed and latched securely, but the rattling sounds like metal on metal and leads me to think (and sounds like) the doors are not closed all the way.

Any feedback would be appreciated.

Thanks!

 

I had a 97 supercab the rubber stops on the door fell out, I replaced it and it stopped the rattle. But my doors rattled even when shutting them and normal driving, not too sure if you're having the same problem but check those.