BATS:JJC   iPathA Series B Bloomberg Copper Subindex Total Return ETN
Copper is a relatively cheap, abundant , and has numerous useful properties such as home construction, electrical wiring, plumbing, to name a few. It's been used for many years as a leading indicator to see where an economy is going. You might want to look at it once in a while to get an idea of future market direction. But just like everything in trading/investing, nothing is guaranteed.