Why does your budgie lick his brass bell?

Budgies are very curious animals, and like to explore things any way that they can. Birds don't have hands, so to touch things they usually use their tongues. A budgie that licks metal objects probably likes the way it feels on his tongue. If it is a big shiny bell, he may be touching his beak to it because he wants to play with the bird he sees in the reflection.