Risk assets have rallied hard in the last 3 days, and many are at or near resistance. It looks like Copper is breaking to upside, along with FCX, which often trades in close tandem with Copper. JJC (Copper ETF) has broken to the upside of its heavily used downtrending resistance, excluding a 2-day pop in early April.
Here is a look at instances in the last 5 years where JJC has accurately (or inaccurately) led the S&P higher or lower. You may need to open the image to get a better look.