Prosody
The art of aligning lyrics, melody, and rhythm so the music supports what the words are saying — the right syllables stressed, the right phrases lifted.
Prosody, in songwriting, is the marriage of words and music. Good prosody means the melody lifts on the words you want emphasized; bad prosody buries important syllables on weak beats or stretches throwaway words over long notes. A line like "I love you" lands when the highest note is on "love"; it falls flat when the high note is on "I".
Three layers matter. Stress prosody: the strong syllables of a word should sit on the strong beats of the bar, or the lyric sounds forced. Pitch prosody: emotionally important words should occupy the highest or most dramatic melodic moments. Rhythmic prosody: the length of a sung syllable should roughly match the length the word would naturally have when spoken — short syllables stay short, long syllables get held.
Listen for prosody in songs you love. The verse-to-chorus melodic lift in "Hallelujah" lands on the title word. The relentless pulse of "Royals" matches Lorde's detached, observational lyric. The wide leap on "Somewhere" (Over the Rainbow) is itself the meaning of the word. Once you hear it, you can't un-hear it — and your own writing will start asking the question on every line: does the music agree with what the words are doing?