Saint Michael the Archangel is not a saint, he is an angel and the leader of all angels and of the army of God.
This is what the title "Archangel" means, that he is above all the others in rank.
Saint Michael has four main responsibilities as we know from scripture and Christian tradition.
Today, Saint Michael, the great defender, is invoked for protection and guidance. He is also the patron of soldiers, police and doctors.
Prayer to Saint Michael
Saint Michael the archangel, defend us in battle.
Be our protection against the wickedness and snares of the Devil.
May God rebuke him, we humbly pray, and do thou, O Prince of the Heavenly hosts, by the power of God, cast into Hell Satan, and all the evil spirits who prowl about the world, seeking the ruin of souls.
Amen
Child version, which we say every day:
Saint Michael the Archangel,
O Prince of God's heavenly army,
Please be my protector against the devil and anything evil.
Thank you for defending me.
Amen