the LORD reigns as the central motif of the Psalter

יְהוָ֣ה מָלָךְ֮
Translation: Yahweh reigns.

I agree with James Mays:

The declaration YHWH malak involves a vision of reality that is the theological center of the Psalter. The cosmic and worldly action to which it refers is the etiology of the psalmic situation. The psalmic understanding of the people of God, the city of God, the king of God, and the law of God depends on its validity and implications. The psalmic functions of praise, prayer, and instruction are responses to it and articulations of its wonder, hope, and guidance. The organizing role of the declaration does not ignore or obviate the variety and plurality of thought about God in the psalms. It does announce a metaphor that transcends and lies behind the variety. It is what every reader and user of the psalms may know as the "code" for understanding all of them (The Lord Reigns, 22).

Indeed, Psalm 93:1 - "The Lord reigns."