What is the purpose of a music video?

We rarely think about why artists release music videos, they're free after all so surely it can't be for monetary gain. Although it technically is, music videos are made to promote the artist and the song they have released. You will often notice that the artist is the sole focus of a music video and there are usually a lot of close ups of the artists face to familiarise the artist to the audience to make the artist easily recognisable. This will mean that audiences are more likely to buy the album if they happen to see it or go to the concert or buy the merchandise.

Below is the music video for Dr Dre - Kush, You can notice that the artists are featured in almost every shot with a lot of close ups on the face.