I use wood for canopies and often that also means adding lights on the wood. For covering plain wood and sealing it against the water which may be spilled, I like to get a bit thicker coat than I can get with spray paint. So my favorite is oil based Rustoleum, brushed on. Once totally dried, so that there are no fumes, either spray or brushed will do the job. My main reason is to get a thicker coat as the canopies do tend to get bumped around and thicker shows the nicks less. User choice there?
But a bigger item might be the heat. Depend on how the light is built but if you are using the metal as both a heat sink and as a mount, it can get pretty hot with LED. Look a bit at how much heat and hw far away from wood it may need to be. Using a horizontal LED bulb in a standard bulb holder placed directly on wood did give me a pretty good black area. Not enough to actually burn but more than I might have liked. A spacer of something that doesn't burn may be a good idea but depends on how hot.