Melody is a uniform succession of single tones and pitches structured as a musical phrase or pattern. Melody includes range, shape and movement, which are key elements in creating a composition or writing a song. Melody helps define where the music is going, from start to finish. Many songs don't have a melody and depend on harmonic chord changes to define the music.
Range is the distance between the lowest and highest tones of a scale. Most composers separate parts of an arrangement by instrument into low, medium or high range. The scale can be major or minor, but range provides room for the harmony and melody. A "narrow range" is defined as a few notes, which the melody revolves around. A wide range could include going into another octave range when composing or playing a piece of music.
When a melody takes a direction or pattern, it is called a "shape" or "shaping." You must know through shaping how to connect melodies and define where the musical piece and composition is going. Shaping also includes passive notes, used between melodic phrases or refrains in music. When combinations of notes ascend upward on a scale, they take the form of an upward shape. Music patterns and phrases that descend are downward shapes.
Movement explains the flow of sound, melody and harmony throughout a composition. A movement can be a conjunct movement, meaning that the melody is played in steps and connected together. A disjointed movement is a melody that moves from octave to octave. In an orchestra, violins can play disjointed patterns of high notes, then patterns of medium pitch notes. Understanding movements is vital to reading music and understanding higher forms of music theory.