The verse is the meat of a song. The function of the verse is to provide a context, provide background information, set the scene or tell a story, establish the vehicle by which the message of the song will be delivered, develop and evolve the story.
The verse gives listeners deeper understanding of the main message of the song and it is the main method of giving a sense of progress through a song.
The first verse establishes the meter (lyrical rhythm), the rhyme scheme for further verses, and the type of language and phrasing to be used throughout the song.
Songs commonly have a number of verses, each composed of several lines. Rhyme may or may not be used within verses, but once established a rhyme scheme works best when it is adhered to.
As the song progresses, each verse further develops the story or theme.