It can be argued that the existence of the angels and other spiritual beings is as evident as the existence of man and animals. Reality and universal wisdom require that the heavens should have conscious inhabitants of their own as does the earth. These inhabitants of many different kinds are called 'angels and spirit beings' in the language of the Religion.
It is true that reality and universal wisdom require the existence of the angels and other spirit beings because the earth although insignificant in size compared with the heavens is continually being filled with and emptied of conscious beings. This clearly indicates that the heavens which resemble decorated castles having awe-inspiring towers are filled with living beings who are the perfect class of living creatures. These b are conscious and have perception and they are the light of existence; these are the angels who like the jinn and mankind are observers of the universal palace of creation and students of this book of the universe and heralds of their Lord's Sovereignty. Through their comprehensive worship they manifest the praises of God by the whole of creation.
The universe requires the existence of the angels because the finely adorned works of art and meaningful decorations and purposeful delicate embroideries displayed in it demand sentient beings who will reflect upon those perfections and praise and commend them in full appreciation. Just as a beauty needs a lover and food is given to the hungry so the food for the souls and the hearts provided through this infinite beauty of art is first of all related to the existence of the angels and other spirit beings. The infinite beauty and majesty of the universe calls for a response which has to be an infinite duty of contemplation and servanthood but since the capacity of the jinn and mankind is inadequate for this duty countless angels and spirit beings fill the great mosque of existence with rows arranged in worship of the Creator. This is what the bands of the angels and other spirit beings do in every corner of the universe. Each band has a duty of servanthood particular to itself. This is implied by some Prophetic sayings and the order of the universe manifests it: some mobile objects from certain heavenly bodies like stars to raindrops for example provide vehicles for the angels who mount them by the leave of God and travel through the material world praising and glorifying God.
Furthermore certain sorts of living bodies provide vehicles for some souls. For example there is a narration that the souls of the people of Paradise enter into 'green birds' of Paradise in the Intermediate Realm--the world of the grave--and travel around Paradise in them and those birds and even some flies are from these groups of living bodies. These souls by the authority of God enter into these living things and observe the wonders of creation through their senses and perform the glorification of the Creator on their behalf. Reality and the Divine Wisdom require this since just as God has breathed life into gross clay and muddy water which have little to do with the spirit and produced numerous conscious beings so too. He surely creates certain sorts of intelligent beings from light and other subtle substances like air and electricity as they are more appropriate for the creation of the spirit and life.