Copper fell up to 1.7% on the London Metal Exchange after it closed in the green for the first time in seven sessions on Friday.
The LME was shut Monday for a UK public holiday. The American military fought off Iranian attacks as it facilitated the passage of two US-flagged vessels through the Strait of Hormuz, while a drone strike hit Fujairah port in the United Arab Emirates.
The risk for metals is a prolonged closure of the strait, which would magnify the energy shock and could force central bankers into a more hawkish stance, hitting manufacturing and crimping demand for industrial commodities. On the supply side, copper stockpiles in LME-tracked warehouses remained near the highest level since 2013, adding to bearish sentiment.
Copper was 1% lower at $12,863 a ton on the LME as of 10:02 a.m. Shanghai time. Aluminum fell 0.9% and zinc dropped 1.1%. Iron ore futures were little changed at $108.40 a ton on the Singapore Exchange, with trading activity subdued due to a China holiday. Chinese markets will reopen Wednesday.
With inputs from Bloomberg
