Research: What is the function of a music video?

The function of a music video is to promote a song that an artist has made. The music video represents the artist and also entertains the viewer at the same time. When artists release a single they normally create a video to go with it, so it can be seen as well as heard in as many places as possible. It's easier for people to remember a song when there is a video to it. They can describe the video and discuss it more and it just promotes the song more.
Some videos are created to add anticipation for an upcoming album release.
Some videos are produced to increase the popularity of an artist or create a better image for them, especially if there is lots of negative press around them at one moment in time. To do this, they normally collaborate with another famous artist and then have a music video directed by someone popular or have famous people in their videos. An example of this is Love the way you lie by Eminem featuring Rihanna.

I think videos are ultimately created to make an artist more popular for one reason or another. Some artists become famous because of the video that is made for their song. For instance, Crank That by Soulja Boy.

He created a dance craze that swept nations and people reacted by them posting videos of themselves dancing to it. Also, it can lead to other people creating songs related to the original, like, Crank That Spiderman by Duffle Bag Boiz ft. The Crank Squad. Another example is Party Rock Anthem by LMFAO ft. Lauren Bennett and GoonRock.