Charles Ellicott Commentary Psalms 18:28

"For thou wilt light my lamp: Jehovah my God will lighten my darkness." — Psalms 18:28 (ASV)

For you will. —Better, You make bright my lamp. In Samuel, It is you, Jehovah, who are my lamp. This obvious metaphor is common in Hebrew, as in all literature. Light is an emblem of prosperity, happiness, or life itself (Job 21:17; Proverbs 13:9, etc.). It happens to be used very frequently of David and his family (1 Kings 11:36; 1 Kings 15:4; 2 Kings 8:19). Compare to Psalms 132:17.