Copper charts for last 18 months on a steep upward curve so maybe they're seeing the turnaround as just the beginning. China about to go on a massive new spending spree all around Asia/Pacific linking ports roads, rail in lots of countries.
https://www.weforum.org/agenda/2017/06/china-new-silk-road-explainer/
https://www.nasdaq.com/markets/copper.aspx?timeframe=18m