“We’re getting the idea that these markets are a lot tighter than many people think, particularly as China continues to do pretty well,” Bart Melek, the head of commodity strategy at TD Securities in Toronto, said in a telephone interview. “The PBOC is saying interest rates are in line with fundamentals, meaning they won’t be doing anything new and they see stability there.”

Copper for delivery in three months rose 2.7 percent to settle at $5,235.50 a metric ton in London. That marked a more- than 20 percent gain from a low in January, meeting the common definition of a bull market. The metal touched $5,250.50, the highest since October 2015.

Eoin Treacy's view

Copper held a progression of lower rally highs for five years but had developed type-2 bottom characteristics since January’s mean reversion rally and is now breaking out. 

I haven’t heard the term Dr. Copper used in years but if such an essential component to economic and, not least, infrastructure development is breaking out, perhaps the outlook for global growth has been underestimated? In the most benign of all scenarios interest rates can drift higher because growth and inflation justify the move.