In Christian mythology, an angel came to mean a benevolent spirit created by God. In Judaism however, it meant literally a messenger of God which could apparently be applied to both human messengers or supernatural messengers depending on the context. The Hebrew word for angel means "messenger", as does the Greek word ἄγγελος (ahn-geh-los) the word from which the English word is ultimately derived. In both mythologies and a few others, there is more or less a hierarchy of angels, although they are not the same and have occasionally changed depending on the author. Many of them only existing in extra-biblical literature.
They perform various tasks, like delivering messages from God to man, acting as executioners and warriors, and protecting humans from harm, and telling God that he is holy.
Only two Angels are mentioned by name in the Christian Bible: Gabriel and Michael. However in the Apocryphal books there are five more: Raphael, Uriel, Raguel, Sariel, and Jerahmeel. Satan is sometimes considered an angel and is featured in the Bible.
- Main Article: Polytheism in Christianity
The belief in many heavenly spirits that can act independently of each other is effectively polytheism. Some Christians believe in angles and usually claim to be monotheists. Muslims avoid this problem by claiming angels do not have free will.
God does not forgive angels
God does not forgive angels that have rebelled 2 Peter 2:4 .  God knew in advance many would rebel, that they would be punished forever and have no chance of forgiveness (unlike humans). That seems rather cruel.
- "Why did God give the angels this choice, when He knew what the results would be? God knew that one-third of the angels would rebel and therefore be cursed to the eternal fire. God also knew that Satan would further his rebellion by tempting humanity into sin. So, why did God allow it? The Bible does not explicitly give the answer to this question. The same can be asked of almost any evil action. "
Some consider that the angels have made an "irrevocable" choice.  However, if they chose to rebel after being obedient, they presumably could chose to obey God again in future. God should have created them so their choice is not "irrevocable" or not created them at all.