Lee Valley sells a wood repair epoxy that after mixing is as thin as a paint. It's meant for strengthening rotted wood. You mix two liquids together, and you have about an hour to apply the stuff to the wood before it begins to harden. That's more than enough time to paint bare metal and have the epoxy self level.

If it were me, I'd probably just paint the epoxy on and leave it to cure without covering it with metal. Microwave ovens use the polarilty of water molecules to create heat within the food. This is why a porcelain dish won't get hot in a microwave oven without any food on it. There's no water molecules in porcelain to vibrate in response to the microwaves. Similarily, a glass of water won't get hot until the water inside it gets hot, but the heat in the glass is the result of contact with the hot water. So far as I know, there's no water in epoxy either, so you should just be able to paint it with epoxy and leave it.

Go to Lee Valley and ask about their two part liquid epoxy for repairing rotted wood.