Psalms 22:29

כִּי לַה' הַמְּלוּכָה וּמֹשֵׁל בַּגּוֹיִם

For the kingship is G-d’s; He is the ruler over the nations.

This is the first of three selections from Psalms used in the Rosh Hashana Malkiyos section. The Vilna Gaon explains the difference between a king (melech) and a ruler (mosheil). A king is accepted by his subjects of their volition; a ruler is imposed upon the people whether they like it or not. Therefore, G-d is King over Israel, who embrace Him in that role, but He is “ruler over the nations” that would prefer things were otherwise.