Let one chord lead to another.

Roman numerals describe chords relative to a key. In a major key, the diatonic triads are I, ii, iii, IV, V, vi, vii°. Uppercase indicates major, lowercase minor, and ° diminished.

In C major, ii–V–I becomes D minor–G major–C major. With sevenths, it becomes Dm7–G7–Cmaj7. Listen to the pull back toward C.

Progression charts suggest common routes, not compulsory rules. A melody can emphasize the current chord tones while drawing other notes from the wider scale.