This psalm celebrates the Lord as King. The Lord is the true King of Israel, its champion and savior. His people sing a new song to celebrate his victory and his faithfulness to them.
The Lord shows his righteous rule to all the nations of the earth. One day, this will lead to a worldwide kingdom of justice (Psalm 98:2, 9). Because of this, all the earth should worship and rejoice together, for the Lord is coming (Psalm 98:4–6).