Why were the Guardian Angels created? Their beauty, their purpose

Creation of Angels.

We, on this earth, cannot have the exact concept of the "spirit", because everything that surrounds us is material, that is, it can be seen and touched. We have a material body; our soul, while being a spirit, is so intimately united to the body, so we must make an effort with the mind to detach ourselves from visible things.
So what is the spirit? It is a being, equipped with intelligence and will, but without a body.
God is a very pure, infinite, most perfect spirit. He has no body.
God created an immense variety of beings, for beauty shines more in variety. In creation there is a scale of beings, from the lowest order to the supreme, from the material to the spiritual. A look at creation reveals this to us. Let's start from the bottom step of creation.
God creates, that is, he takes everything he wants out of nothing, being omnipotent. He created inanimate beings, unable to move and grow: they are minerals. He created plants, capable of growing, but not of feeling. He created animals with the ability to grow, move, feel, but without the power to reason, endowing them only with a wonderful instinct, for which they remain in existence and can achieve the purpose of their creation. At the head of all these things God created man, who is a being composed of two elements: a material one, that is, the body, for which he is similar to animals, and a spiritual one, that is, the soul, which is a gifted spirit of sensitive and intellectual memory, of intelligence and of will.
In addition to what is seen, he created the beings similar to himself, Pure Spirits, giving them great intelligence and strong will; these Spirits, being bodyless, cannot be visible to us. Such Spirits are called Angels.
God created angels even before sensitive beings and created them with a simple act of will. Endless hosts of angels appeared in the Divinity, one more beautiful than the other. As the flowers on this earth resemble each other in their nature, but one differs from the other in color, perfume and shape, so the Angels, despite having the same spiritual nature, differ in beauty and power. However the last of the Angels is far superior to any human.
The Angels are distributed in nine categories or choirs and are named after the various offices they perform before the Divinity. By divine revelation we know the name of the nine choirs: Angels, Archangels, Principalities, Powers, Virtues, Dominations, Thrones, Cherubim, Seraphim.

Angelic beauty.

Although the Angels do not have a body, they can nevertheless take on a sensitive appearance. In fact, they have appeared quite a few times cloaked in light and with wings, to manifest the speed with which they can go from one end of the universe to the other to carry out the orders of God.
St. John the Evangelist, rapt in ecstasy, as he himself wrote in the book of Revelation, saw before him an Angel, but of such majesty and beauty, for which he believed God was himself, prostrated himself to adore him. But the Angel said to him, "Get up; I am a creature of God, I am a fellow of yours ».
If such is the beauty of only one Angel, who can express the overall beauty of billions and billions of these most noble creatures?

Purpose of this creation.

The good is diffusive. Those who are happy and good, want others to share in their happiness. God, happiness in essence, wanted to create the Angels to make them blessed, that is, partakers of his own bliss.
The Lord also created the Angels to receive their homages and to use them in the implementation of his divine designs.

Proof.

In the first phase of creation the Angels were sinful, that is, they were not yet confirmed in grace. In that period God wanted to test the fidelity of the heavenly court, to have a sign of particular love and humble subjection. The proof, as St. Thomas Aquinas says, could only be the manifestation of the mystery of the Incarnation of the Son of God, that is, the Second Person of the SS. Trinity would become man and the Angels would have to worship Jesus Christ, God and man. But Lucifer said: I will not serve him! - and, using the other Angels who shared his idea, waged a great battle in heaven.
Angels, willing to obey God, led by St. Michael the Archangel, fought against Lucifer and his followers, shouting: "Salute to our God! ».
We don't know how long this fight lasted. St. John the Evangelist who saw the scene of the celestial struggle reproduce in the vision of the Apocalypse, wrote that St. Michael the Archangel had the upper hand over Lucifer.