Mikhael is the God of Destruction, and he's located in the "Eye of Mikhael", a jem that Teito's father hid in his right hand when he was a baby. The power of Mikhael is the one that only the successor of Raggs Kingdom can hide in his body, and since that moment Mikhael was sealed like in an eternal dream.
But Mikhael can feel Teito's feeling. He can see his heart and for this reason he'll never hurt someone that he loves, because he considers him his master.
An example is the thanksful that Mikhael gives to Hakuren to be friend of Teito, or the desire of killing Ayanami, that he possesses since the murdered of Teito's father and best friend.
His personality is childish and oddish, he's the kind of person that always wants to be right, even if it could be means "make abuse of power". He's very loyal to his master and maybe his fear is to be alone, because Teito feels his sadness in a prove for the exam to be Bishop.
In a funny drama CD Mikhael drinks Frau's saké and takes the control of Teito's body, so we can say that he loves to drink alcol! XD
Acting consequentially he makes all crazy, especially Frau and Hakuren! XD