My impression is that they appear to humans in human form, but are spiritual and not physical beings as humans are. The fallen angels are those who mated with humans [humankind]. We mortal beings are the descendants of these fallen spiritual beings, and this accounts for the difference between us and our animal relatives. The angels in heaven are like us, but have never yet manifested on the material plane of existence. There are those among us who have recived special missions here, but usually although aware of their mission, they are not aware that they are angels. They have no free will, as an odinary human being. It does not matter what rligious indoctrination they have been exposed to they are here to do the will of God only, and exist to be of service to humanity. God's messengers are everywhere, and exist to be of sevice, but they are not allowed to interfere with the free will of mortals.

Jesus of Nazareth is said to be 'the Prince of the Angels', and Mary is said to be the 'Queen'.