All creation is in a relation of servant-master, child-father, dependent-sustainer.
This applies to all of creation, including the Seraphim and Cherubim, and the Theotokos, and the Saints. We all have much in common, as being created beings, and share the same relation to God in regard to our createdness.
It is part of the proper state of being for all creation to be sustained BY God, and to minister TO God. This is not because God needs to be ministered to, but because our createdness is fulfilled in service to God, in worship and obedience.
We do not minister to God best when we are sinful, even if we feel bad about ourselves, and therefore the Cherubim and Seraphim, and the Theotokos and the Saints, are examples to us of how we should aspire to minister to God, not only by words and deeds but by the disposition of our hearts at all times.
Psalms 123:2 Behold, as the eyes of servants look unto the hand of their masters, and as the eyes of a maiden unto the hand of her mistress; so our eyes wait upon the LORD our God.
Thank you! This helps A LOT!