This is a fundamental question. However, using the terms “love” and “slave” in the same breath seem to reflect confused ideas of both.
Unfortunately, the term “love” has been totally shot in the English language: I love my wife, I love my father, I love my mother, I love my brother, I love my sister, I love my son, I love my daughter, I love my country, I love chocolate, I love rock & roll, I love “24”, etc., etc., etc. All different forms of human love. The love I have for God should be similar to the forms towards the beginning of that list of examples, but unique, still.
Is each of us inferior to God? Like it or not but even a complete fool would admit he is. But too many fools still bristle at the notion of being inferior to anyone or anything. Does the “inferior” relationship I have to God make me a slave to God? No. At least not the God of the Jews and certainly not the God that Christ manifested to us. Islam - the religion of submission and surrender - might call me to be a slave to Allah but thank God I was not born into that heritage.
There are many but clearly one key to understand that I am not a slave to God is that I have free will and at full liberty to refuse him. Our love is fully voluntary.
If you think that entering voluntarily into a wonderful, fatherly, fully benevolent relationship with God is enslaving oneself, I think the term is being misused. In the past, some have volunteered themselves into servitude in exchange for the security of ownership by someone else. The fact that in nearly all civilized societies even voluntary slavery is outlawed bespeaks to the fact that slavery is not wholesome in any form and announces the equality of men.
But to equate my dedication to my wife, my parents, my children, my country, the welfare of my fellow men, etc., as slavery to each of these is to twist to the absurd the whole nature of love. It is not unlike radical feminists calling all marriage slavery.
As I said in the beginning, using the term love (inherently voluntary) in the same context as slavery (never voluntary) reflects a misunderstanding of the difference in the terms. That God, as our vast superior, COULD demand us to be slaves and has chosen not to says clearly that he does not wish us to be slaves but his children, his brother, his friend.
I suppose you could say, but the consequences of a refusal of this relationship are so severe that it amounts to extreme coercion. What sort of offer is that? Not one of love.
To answer this, you have to look at some other terms - like justice - an often forgotten concept.
And the fact that God has been so very coy about this undermines any firm assertion the consequences are dire. In fact, isn’t denial of the reality of hell the norm of all “smart” people? Remember the rich man and Lazarus - and the rich man’s brothers? I’m sure if I were given the vision of hell given to the children of Fatima my life would change overnight.
No. God loves me. I am not his slave. I freely love him. But not enough.