Optimal monk usage for a newbie?

Hi there,

I am a newbie (well i have been playing for 2 years but I still consider myself a noob since you guys average much more than that ;)) and something I haven't been using in my games yet is the monk. Whenever I have built it I have failed defending it or just used it to get relics. As far as I understand it is a really good military unit with its conversions but I haven't got around of how to actually use it wisely. I wonder if you have any ideas of how to optimally use the monk?