Angels are spiritual, immortal, non-corporeal beings. They are Messengers and Servants of God. They have free will and choose to serve God unceasingly, seeking always to glorify Him. Angels are not human beings and human beings do not become Angels, Angels are the Protectectors of human beings. Scripture and Tradition tells us that in the hierarchy of Heaven there are 9 Angelic Orders, as follows:
The Nine Angelic Orders
Seraphim
Cherubim
Throne
Dominations
Principalities
Powers
Archangels
Angels
Catholic Teaching about Angels
Angel Popularity on the Rise
Angels are a Truth of Faith
Angels – by Fr. John Trigilio
Angels – by Fr. William Most
Angel – by Hugh Pope – Catholic Encyclopedia
Angels A Biblical Perspective by Jean Kincaid, Ph.D
Angels: fiction and Facts – by Bill Dodds
Angels in the Catechism of the Catholic Church
Angels in the spirituality of Saint Louis de Montfort
Angels in Scripture (not exhaustive)
Gn 3:1-15 The fallen Angel Satan, tempts Adam and Eve to sin.
Gn 22:1-18 Abraham is prevented from sacrificing his son, by an Angel.
Mt 4: 1-11 Christ is tempted by Satan, but the Angels tend to him.
Mt 28: 1-7 Jesus’ Resurrection is announced by an Angel.
Rev 12:7-9 St. Michael the Archangel defeats Satan.
Angels in the Catholic Catechism
CCC 328-395
Read these Catechism paragraphs here
