Purpose of a music video

Promotional
Extension of income
Extension of outlets(music channel, direct dvd, CD sales)
Synergy

Promotional
Advertisement
Illustrates the song
Appeals to visual audience
Expresses an individuals emotions
Tells a story
markets an image
Creates a brand

A "successful" music video would be Michael Jacksons 'Thriller' in 2006 it was listed as the most successful music video by the guinness book of world records. in 2009 the video was inducted into the national film registry of the library of congress, the first music video ever to achieve this honour.



Another example would be Stan by Eminem

This is a rather extreme example, the 'protagonist' Stan wants nothing more than to be like his idol Eminem to the point of styling his hair the same way and disliking his own name.
he continues to write fan mail to Eminem though due to bad luck the mail never reaches his idol and it starts to drive Stan to the point of suicide and taking his partner with him.

"Hurt" by Johnny Cash is quite the emotional example as well.


Both Cash and his wife were in poor health at the time of filming and June Cash would pass away three months after filming with Johnny following seven months after filming.
the way he sings the lyrics lets you know that he knows his time is up which is what gives this song such an impact, making it possibly the saddest music video to exist.