We know Angels exist because The Old Testament mentions them at least 108 times. The new Testament mentions them 165 times, of which I will quote
“ For by Him all things were created both in the heavens and on earth, visible and invisible, whether thrones or dominions or rulers or authorities- all things have been created by Him and for Him. And He is before all things and in Him all things hold together. ”
We don't know when these Heavenly spirits have been created, but we do know that their number is huge. (Matthew 26:53).
They are God's messengers and they don't have bodies, like us, humans.
According to Hebrews 1:14, they are spirits in God's service, to serve those among us who will gain salvation. They have some attributes that we human beings do not possess.
Sometimes, when they appear to men, they may take on our appearance. In the book of Genesis we can read how three of these heavenly creatures have appeared to Abraham looking like common travelers. But that is not necessarily always the case.
For instance, Daniel saw a Heavenly Spirit with arms and legs like polished metal and precious stones, with a face like lightning!
Or think about the celestial being who rolled back the stone from Christ's tomb: he was radiating a dazzling light! Indeed, they are not monotonous beings!
Sadly enough one third of these heavenly spirits became demons by disobeying God. They rebelled against their Creator under the guidance of Satan, also called the old serpent.
They lost their holiness, but not their capacities.
We must be cautious about celestial beings, because demons can disguise their appearance and deceive us.
The first Choir, the Seraphims is the highest rank. They have the privilege to proclaim God's Glory on and on!
The Cherubim, the second Choir is manlike in appearance, with the exception of their two wings. They guard God's glory.
The Thrones, also called Elders, are living symbols of God's justice and authority.
Then we have the choir of Dominions, who regulate the duties of the lower celestial beings. They also preside over nations.
The Virtues, mighty receptors of the Divine Illuminations granted to them; they never fall away from the Divine Life.
When we take a look at the Powers or Authorities, we understand that these are also warrior spirits, completely loyal to God.
The Principalities, shown wearing a crown and carrying a scepter, collaborate with the Powers.
Then, pertaining to the choir of Archangels, our heavenly messengers, we know:
The last Choir is the lowest order and the most recognized. There was a multitude of them to announce the birth of Jesus! We know them better as our Guardian Angels. Dear sisters and brothers in Christ, we are warned not to worship these Heavenly beings, but they certainly can assist us in fighting the battle against the devil and all his temptations.