At the heart of every song is the melody. The melody is a mix of tones and rhythmic patterns. In order to create a melody there needs to be a musical scale. The scale for the songwriter is like the pallet for the painter. The painter has on the pallet various paint colors that can be mixed to create new colors that are added to the canvas to render a picture.
Armed with the knowledge of the notes in a musical scale will help you write melodies for your songs. Obviously there is a lot more involved in writing a great song melody. Having an understanding of a musical scale is a vital thing every songwriter needs to know and understand