If layers of paint are hiding your beautiful metal door plate, strip the paint with solvent using a brush in a well ventilated area.
Safety Note: Eye protection is crucial when applying chemical solutions.
One classic method of removing paint from metal fixtures is to remove the hardware and soak it in hot water with a little detergent. After an hour or so, the paint should be dissolved to the point it can be brushed off. Use a nylon scrub brush to clear off any stubborn sticky bits.
Additionally or alternatively, you can clean and polish the hardware with a high speed rotary tool, using a polishing compound like beeswax to bring out the gleam. Spraying the hardware with lacquer will help it maintain its luster.