Some angels are given proper names to denote the service they are empowered to perform. In a homily about the Archangels, St. Gregory the Great gives us the meanings of the Archangels' names and more.
Nearly every page of Scripture witnesses to the fact that there are angels and archangels. The prophetic books speak of cherubim and seraphim. Four more orders are enumerated by Paul the apostle when he says, "Above every principality and power and virtue and domination." And again, writing to the Colossians, he says, "Whether thrones or powers or principalities or dominations."
It must be realized that "angel" is the name of their office, not of their nature. For the holy spirits of the heavenly homeland are always spirits, but they are angels only when they are announcing something.
Those who announce things of highest importance are called "archangels". These archangels are also given special names to describe their particular virtue. Michael means, "who is like unto God?" Gabriel means "strength of God," and Raphael, "medicine of God."
Whenever something is to be done needing great power, Michael is sent forth, so that from his action and from his name, we can understand that no one can do what God can do. Hence that ancient foe, who through pride desired to be like God, saying, "I will scale the heavens, I will set up my throne, I will be like the most high," is shown at the end of the world destined to fight with Michael the Archangel.
Similarly, Gabriel was sent to Mary. He who was called "strength of God" came to announce the one who appeared as a humble man to quell the cosmic powers.
And Raphael is interpreted, as we said, "medicine of God". For when he touched the eyes of Tobias to do the work of healing, he dispelled the night of his blindness.