Adam was in a special sense the son of God. "Which was the son of Enos, which was the son of Seth, which was the son of Adam, which was the son of God." Luke 3:38. He was a son of God in a different sense from what we are.
The Scripture says, "Beloved now are we the sons of God." But we are the sons of God by re-creation; Adam was the son of God by creation in the first place. He was set here to have dominion over this part of the universe as God's representative.
"And God said, Let us make man in our image, after our likeness; and let him have dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over every creeping thing that creepeth upon the earth." Genesis 1:26. God made Adam His premier, and placed the dominion in his hands, recognizing him as His representative in this earth.