I've been writing a lot lately about copper. Many have dubbed it "the metal with the PhD in economics" due to its widespread use in many phases of the economy. Think electrical wiring, plumbing and pipes, air conditioning and heating, cookware, computer circuit boards, medical imaging and making brass.
Anyway, the point is that when copper prices fall it is due to perceived future demand from the economy falling off. If you look at copper trading today, the economy is in for some trouble.
Check out this giant metals miner - BHP Billiton. That is a completed weekly double top. I don;t care if the market came back to close positive today, things are weak.