Do your airframe hole plugs look like this?

My sympathies if they do. This is a great way to get dissimilar metal corrosion in your airframe. Over time the metal plugs (left unpainted) can tend to rust as well. While the Home Depot/Lowes metal plugs look nice and shiny when new and are quite tempting, many folks suggest that plastic plugs would be a good alternative.

Just be careful of placing them topside where they can be exposed to the UV rays of the sun, as many common plastic plugs do not contain UV stabilizers, they will embrittle and yellow over time. Less of a factor if your plane is hangared most of the time.