A song is a musical composition for the human voice characterized by a melody to which words are placed. The music may be purely instrumental, as in the case of an aria or a recitative from classical music. It may also have lyrics, as in the case of a romance or a folk song. The lyrics may be written for or set to a particular piece of music, as in a romance, or they may be written without music, as in a free verse.
Songs serve many functions in society; they can relieve boredom, fill uncomfortable silences, promote social cohesion and communication or even help regulate emotions1. They also vary greatly by genre, with rap songs not sounding like Country songs, and Country songs not sounding like East Indian Bhangra.
For popular songs to be successful, they must appeal to a wide ranging audience, and this is often achieved by including elements from multiple genres. For example, pop songs often include elements of rock, soul and electronic music.
If you want to write a great song, try to stick to lyrical subjects that are of interest to most people. This will make the song more memorable, and it will be easier to get your audience to give the song a second listen when they hear it again.