Priming metal and plastic access point covers
Scuff it up with a green Scotchbrite sponge or pad, merely to knock the gloss off the paint.  That is paint.    Very important, this step! 
Wipedown any dust or grease. 
Prime it with a primer that reasonably matches the color of the proper you used on the adjacent walls.  This is a very important step.  First choice is an alkyd primer such as Rustoleum 7780 Clean Metal Primer (they recently changed the number) or Kilz will do in a pinch.  Second choice is a latex primer, but only use this if you are very sure about your work in steps 1 and 2. 


Primer is important because paint cans lie. There is no such thing as primer-paint.  Background colors DO print through paint, especially the near-white pigments used on almost all architectural coatings.  If you want the topcoat to match, the underlying primer color must also match.  Primer's job is to provide a uniform surface that is the same in absorption, texture, chemical interaction, and color, so that topcoat comes out equal in all locations.

By applying a separate primer, you are able to force the surfaces to be equal by adding primer coats wherever a background color is still printing through the primer.  When the primer job is complete and even, that means the 1-2 coats of topcoat will print through, but they'll print through consistently.