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 a 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.