Many entry doors have an aluminium threshold. Aluminium is a durable metal that doesn't rust. For this reason it is a standard product. However, there is a current trend in home finishes that favours bronzes and other darker metallics. To achieve this look it is necessary to paint over the aluminium. It's important to consider that a painted threshold will not wear as cleanly as the aluminium will on its own. But, if you are willing to repaint every few years, then you can transform the look of your threshold with a little work.
Scrub the threshold with a small wire brush (brass works well). It is important to remove all ground-in dirt from the tiny crevices and in the corners adjacent to the wood mouldings.
Vacuum the debris. Keep brushing the threshold until you are certain all of the grit is removed.
Scrub the threshold with soap, water and an old toothbrush. Use a sponge to remove the dirty water and residues.
Sand the threshold with 220 grit sand paper to rough up the surface and to remove any additional materials. Repeat step three. Dry the threshold thoroughly. At this point it should be very clean and ready to paint. Wipe the threshold with denatured alcohol to remove any oils acquired from touching the threshold with your hands.
Tape off and prime the threshold. Often you can find aluminium specific primer in spray cans. Simply protect surrounding areas from overspray if you use a spray product. Apply at least two coats. Spray coats usually dry within an hour.
Apply an epoxy paint made to cover aluminium in the paint colour of your choice. Keep in mind that this is a high traffic area. Allow the paint to dry, and apply additional coats. Check the manufacturer's directions for drying time for your epoxy choice.
Epoxy paints are used on high traffic floors, and they hold up fairly well if the surface is well prepared and the epoxy is applied properly.
Make sure you do this project at a time of the year where the door can remain open for a few days without people needing to use the doorway.