Oh by the way...the pic of yellow drippy paint is not mime but a really cool photograph(sadly the person didn't leave a way for me to give her credit). Love you whoever u r.
Here is what you need:
Sandpaper (200 grit or whatever you have on hand is fine)
Spray paint for metal(I used all purpose paint from Rustoleum in satin black)
Remove the knob & lightly sand the entire piece.Wipe clean of any dust and in a ventilated area spray the primer on, wait an hour, and then put the spray paint on lightly, wait another hour and then put another light coat of paint on. Take you time with the spray paint, keep your distance about 6-10 inches from the hardware and you'll end up with a nice finish.
Spray paint is available in so many finishes. They have a paint that gives you a hammered finish which I haven't tried but it looks fab. The copper looks awesome too. Even painting a pretty image like these lemons add pop to this door and is a different place to add interest.