Jesus main reason for coming to the earth was to rule the kingdom. Matthew uses Kingdom of heaven while the other gospel writers, in similar stories and parables, use Kingdom of God. Matthew also uses Kingdom of God several times. All scriptures are from the King James' version Bible. Some truth to these, but Kingdom is more.
Kingdom is now within the believer.
So likewise ye, when ye see these things come to pass , know ye that the kingdom of God is nigh at hand . Eternal - Always existed. God rules the heavens. Earthly - God always planned for a Kingdom on the earth with Jesus as the King. And I will make thee exceeding fruitful, and I will make nations of thee , and kings shall come out of thee .