My answer is
An American brand of shampoo, I'm quite the work of art.
A bust is a sculpture of a person that includes just their 'head and shoulders'.
I come with a boom and can sadden your heart.
In economics, bust and boom are opposites. A bust is usually marked by a period of depression.
You'll find me when you reach not 21, but more.
In Black Jack, if you go over 21, you go bust.
I'm measured and sometimes even lusted for.
A woman's chest measured around her breasts is her bust.
I'll also be there when you're caught doing wrong
A police raid or search is known as a bust.
and I'll happen on the dance floor during a song.
'Bust a move', which means to dance.