The word "King" is translated. "a chief ruler, one invested with supreme authority over a nation, tribe or country." --Webster. In the Bible the word does not necessarily imply great power or great extent of country. Many persons are called kings whom we should rather call chiefs or leaders. The word is applied in the Bible to God as the sovereign and ruler of the universe, and to Christ the Son of God as the head and governor of the Church.
Every Kingdom that is established is governed by a King. Today we are goveren by a soveriegn King, whose name is Yeshua (Jesus), who is established by the royal command of Yeweh (the Father).