Forum:Control of opponent monster.....

On many YuGiOh cards, the effect is to take control of an opponent's mosters, such as with Brain Jacker. My question is......what can you do with the monster, according to the rules? Can you use it for a Tribute Summon? Attack your opponent's other monsters???

Any help would be appreciated.

Also, I have a question about the trap Mirror Gate. Is it just me, but since you switch control BACK at the End Phase, isn't this card a waste, or do I just not get it??