The most-traded June copper contract on the Shanghai Futures Exchange ended little changed at 43,830 yuan ($7,062) a tonne on Monday. The Shanghai Futures Exchange's (ShFE) new nickel contract fell 4 percent during its second day of trade, before ending down 2.7 percent at 98,430 yuan ($15,860) a tonne.
"A weak macroeconomic environment and demand data out of China in combination with worries about the Malaysian tax gave enough ammunition for the shorts to come in," said Daniel Hynes, a strategist at ANZ in Sydney.
Demand for nickel pig iron in China did not pick up as strongly as expected after the Lunar New Year holidays, industry sources said last week, with stainless steel producers set for lower exports as the sector faces tariff barriers.
The European Union is preparing to impose anti-dumping duties on imports of stainless steel cold-rolled sheet from China and Taiwan, while India is also considering similar action.
In Malaysia, which stores almost half of the LME's nickel inventories at around 210,000 tonnes, a new government tax may force owners to sell metal rather than bear the cost of transporting stocks to nearby LME locations, Hynes said.