The condo board just replaced my old wood door, with a sheet metal door. both having windows. I need to hang blinds and the kit does not have metal screws. Will my blinds be secure enough if I drill wood screws into the metal door?
If necessary any screw will secure the brackets to the door (in most cases). The reason to use sheet metal fasteners is to penetrate the metal door skin. Once the tip of the screw is past the metal surface it grabs and drills into the wooden frame work. The wooden skeleton of the door is the 4 outside edges and the 4 sides of the window. Your best bet for successfully attaching to the wood frame is to remember the frame extends about an inch wider than the windows perimeter. Keep your brackets (if possible) under an inch past the windows edge. It's the wood framing that is supporting the brackets. So if you drill an opening in the metal skin any screw will suffice.
If you can't hit wood, usually just the top inch of the door, you're going to have to do a through-the-door screw & nut setup (like for a peep hole). The metal skin is not enough for an operable blind. Nuts inside the blind brackets is best, but the only other option for through-the-door is to use Tee Nuts on the outside & screw into those. Of course, get the right length screws or cut them down after installation...hacksaw, dremel or bolt cutter, whatever you have room for.
Drill a small hole and use a nail to find out how much wood behind the metal. If little wood, do not use wood screws, or you will strip the metal or the screws.
I would drill the holes slightly smaller than the diameter of the metal screws (finer thread) you will use. Then get an extra set of metal screws and file the tip a little into a taper. Use your drill with firm pressure at slow speed to tap the metal, just half way.
Throw away the tapered metal screws you used to tap the metal holes. Now you can mount your fixture with the second set of metal screws, using a screwdriver for the last few turns as you don't want to strip the metal, easy to do with an electric drill.
Of course, if you have plenty of dense wood behind the metal, drill a shallow hole through the metal and an undersized hole into the wood for wood screws.
Hope this helps.