We learn about angels from Scripture. In Sacred Scripture, we learn that there are 9 "choirs" of angels as well as others who are mentioned. These 9 choirs include:
Seraphim, Dominions, Principalities, Cherubim, Virtues, Archangels, Thrones,Powers and Angels.Other angels mentioned in the bible include the "Angel of the Lord", Guardian Angels, the Angel of Gethsemane and the Angel of the Resurrection.
Angels' function in creation is to stand before the throne of God as part of the court of heaven. They are to praise God and minister to Him for all eternity.
A second function of angels is as God's holy messengers. The Bible gives us many examples of this. An angel announces the birth of Sampson, Isaac, John the Baptist and Jesus Himself. An angel brings comfort to Joseph, when he is concerned about Mary's unexpected pregnancy, and to Jesus in the garden of Gethsemani.
The third function of angels is as personal guardians--our guardian angels. Since we each have our own Guardian Angel, there are always angels all around us, especially during Mass. Wherever Jesus is, in His Real Presence, angels abound.
Saint Padre Pio used to send his angel on erands of mercy to others. We can ask our own guardian angel, and others' to pray for us before the throne of God. The next time you are in the presence of someone "challenging", pray to their guardian angel (and your own) for strength and support.
The book of Revelation mentions angels in a context that sounds remarkably like Mass.
And another angel came and stood before the altar, having a golden censer: and there was given to him much incense, that he should offer of the prayers of all saints, upon the golden altar which is before the throne of God.
And the smoke of the incense of the prayers of the saints ascended up before God from the hand of the angel.