Copper futures at New York’s Commodity Exchange fell by more than 22% - the highest ever, as traders recalibrated the value of metal in the US versus the rest of the world.

The Trump administration says that the tariffs on metals imports are aimed at boosting domestic industries and addressing "trade imbalances."

Copper traders were caught flat-footed after refined copper was exempted from Trump's new tariffs. The exemption triggered a 20% drop in copper futures on the COMEX exchange. Traders now face excess inventory, with COMEX stockpiles at a 21-year high.