Watch the Puzzling Melodies from Lyrics online guitar lesson by Matthieu Brandt from Songwriting on Guitar
Some composers will start with lyrics when they write a composition. These lyrics, poems, expressions can give you an initial idea about the flow of the melody. A rhythmic analysis of the phrases and experiments with stressing words within the phrase, can be a jump board for a logical sounding melody. A great way of finding a melodic contour that fits your lyrics is using the speech patterns and stress when you just say your phrase out loud. Stressed words will almost always be higher in pitch than the surrounding words and the general contour of the phrase can rely on this. The use of chord tones will make a word/syllable flow with the underlying harmony and generally create a stable sound. Non chord tones will give the word some energy.
By stepping back from the composition and thinking about stress, stable and unstable notes, lenghtening syllables, swallowing certain sounds, you can get more information about HOW you say things. Or in this case how you sing your lyrics. Before your audience starts listening to the words you sing, they will first try to grab the rhythm of your vocals. Then they'll try to capture the melody itself and only AFTER they will actually hear the words. HOW you sing it is more important than WHAT you sing.