St. Michael is one of the principal angels; his name was the war-cry of the good angels in the battle fought in heaven against the enemy and his followers.

Following these Scriptural passages, Christian tradition gives to St. Michael four offices:

To fight against Satan.
To rescue the souls of the faithful from the power of the enemy, especially at the hour of death.
To be the champion of God’s people, the Jews in the Old Law, the Christians in the New Testament; therefore he was the patron of the Church, and of the orders of knights during the Middle Ages.

To call away from earth and bring men’s souls to judgment ("signifer S. Michael repraesentet eas in lucam sanctam", Offert. Miss Defunct. "Constituit eum principem super animas suscipiendas", Antiph. off. Cf. "Hermas", Pastor, I, 3, Simil. VIII, 3).

Regarding his rank in the celestial hierarchy opinions vary,place St. Michael over all the angels; they say he is called "archangel" because he is the prince of the other angels; others believe that he is the prince of the seraphim, the first of the nine angelic orders. But, according to St. Thomas (Summa Ia.113.3) he is the prince of the last and lowest choir, the angels. The Roman mytology seems to follow the Greek mytology, rome calls him "Princeps militiae coelestis quem honorificant angelorum cives". Some peoples places St. Michael even above the Twenty-four Elders. The Greek Liturgy styles him Archistrategos, "highest general"

It would have been natural to St. Michael, the champion of the Jewish people, to be the champion also of Christians, giving victory in war to his clients. His prestige as angelic healer obscured his interposition in military affairs. It was from early times the centre of the true cult of the holy angels, particularly of St. Michael.