How to smooth or sand the chipped metal door?

Wanda, you need to keep sanding with finer grits, so if you started with say 60grit, you work your way up to around 400 grit or so. You need to start with a coarse grit and work up. Don’t put a lot of pressure on the sandpaper and do use a block to keep it even. If you’re still having trouble, or there’s a ding, mix up a very small amount of bondo and apply it where the paint is missing. Don’t worry about fine scratches, your paint should fill those areas.

I agree with Elaine. You need to start with a course sandpaper to get rid of the loose paint before going to finer grit sandpaper. The fine grit will only help smooth it out a little and break the surface for the paint to stick, the courser grit is the work horse that will get rid of the loose and start the smoothing process. Make sure to clean it well once you are done to make sure you get a really clean smooth surface. I would suggest using spray paint made for metal in thin coats so you don't get drips or brush strokes. We painted our metal screen door with Rustoleum and it turned out great! We laid the door on saw horses and put new paper on the windows taped down with painters tape. Good luck with your sanding and painting, Wanda!

It sounds like the sandpaper you’re using isn’t fine enough. You can get sandpaper all the way down to 400-grit, 600-grit, and even finer. You won’t be able find it at your local home improvement center, you’ll probably have to buy it online.

When you’ve satisfactorily sanded it, then prepping it for painting and the paint itself are worth the time and money to do right. Factory painted steel doors are sprayed with enamel. Painting them with latex house paint is not a long term solution. I’d use alkyd oil based enamel.

In any case, repainting requires removing the door and it’s hardwate, cleaning, repairing, sanding, priming and then painting two coats.