The key to painting metal is to clean it really well (I use TSP substitute), then spray the paint with very light coats (five or more will do). Believe it or not, the hardest part was getting the knocker back onto the door (tape wouldn’t hold it in place while I screwed it in, so I had Dad help while he was over helping with the first exterior coat of paint).
It’s a far cry from what this old door used to look like:
Now I have a door knocker that matches the light fixture and the new (old) house numbers that got the same paint treatment. Matchy-matchy may not work well all the time for interior decor, but it certainly looks good on the exterior!