If you want to understand what exactly a Christian BECOMES and why calling Christ “Lord” is such a privilege then you have to understand “divine adoption.”
The heart of the Christian life is Galatians 3:26. “ So in Christ Jesus you are all children of God through faith.” YOU ARE ALL CHILDREN OF GOD. We already ARE his children.
We are not God’s children in a general way by virtue of being His creation, though it is true that there is a sense in which all human beings are God’s children because we have all been made in His image.
Paul speaks of a deeper relationship. We are His children by virtue of being “in Christ Jesus…through faith.“