How do we know angels exist?
The Scriptures give us no indication of the precise time of the creation of angels; their existence is assumed at the earliest times. Our Lord often spoke of angels; in the New Testament they are numerous and seven orders are mentioned: Angels, Powers, Principalities, Dominions (ations), Thrones and Archangels the Old Testament specifically mentions two others Seraph (im) and Cherub(im).
God bestowed upon angels great wisdom, freedom, and power, and their many appearances in the New Testament are indication of the lead role assigned to them. Both the New Testament and Old Testament refer also to the fallen angels. The Temptation of Adam and Eve presupposes the existence of bad spirits or demons who were cast into hell from which they have no hope of redemption.
Angels are purely spiritual or bodiless persons (Mt 11:30), some of whom behold the face of God and thus are in bliss (Mt 18:10). These spiritual beings comprise the celestial court and are called angels (from the Greek for "messenger") because, according to the Bible, they carry out missions at God's command. In order to complete these missions, they can at times assume bodily form.
According to the Bible, their missions are sometimes of great importance - eg, the Annunciation (Lk 1:26; 2:9-14). Like us , the angels are the objects of God's grace and love. But because, unlike us they are non-bodily creatures, their response to God's love did not require time and reflection to grow and mature. As soon as they were created and received grace, they had the opportunity to respond to God's love and thus be welcomed into bliss. While many did so, some did not. Perhaps the most significant continuing activity of the good angels is to be the agents of God's particular providence for mankind. Thus, the Church teaches that everyone has a guardian angel, based on references to them throughout the Bible.