In a magical video where Google's head of search spam, had his body removed all to make a point that the body of a page's content is really important.
Yes, Matt actually removed his body, in a way to show just how important the body is. The head alone, while important also, is not enough, you need a good and fit body to go along with your good and fit head.
In short, title tags, meta descriptions, and the rest of what you put in your header on your web pages are important. But so is the body content and you need to make sure both are high quality, unique and useful.
Here is the video:
Forum discussion at Google+.