Losses were limited, however, by expectations of further stimulus by global central banks to rein in faltering economic growth and help lift metals demand.
Copper's losses represented the fourth decline in five days as the market came off a peak largely spurred by a surprise deal by European leaders on June 29.
Three-month copper on the London Metal Exchange shed 0.93 percent to end at $7,490 a tonne after touching an intraday low of $7,4828. Copper rose 0.4 percent on Monday.
"There's been some responses by central bankers to deteriorating conditions (and) we've had some positive news flow out of Europe, but I wouldn't call this a strong market at all," said Deutsche bank analyst Dan Brebner.
"Growth is going to remain sluggish over the next couple of months with the possibility of further deterioration in the US and China, and my expectation is this will continue to weigh on metals markets."
Euro zone finance ministers agreed a deal overnight to release 30 billion euros ($36.9 billion) of bailout funds to help Spain's banks by end-July, but the euro failed to gain traction in response to the news, indicating investors remain wary about Europe.
A weak euro makes dollar-priced metals more expensive for European investors.
Also weighing on copper, Tuesday's trade data showed China's imports of copper fell 17.5 percent to 346,223 tonnes in June from 419,741 tonnes the month before.
The broader Chinese trade data also raised concerns. Total imports were curtailed in June, in further evidence that Europe's three-year-long debt crisis is dragging down economic activity around the world.
Markets are now awaiting China GDP data due later this week, with many pegging hopes that weak numbers will herald another round of monetary easing by central banks.
Recent comments from central bankers have raised hopes for stimulus. Three top US Federal Reserve policymakers called for more quantitative easing.
RAYS OF HOPE
Since the beginning of May, copper has lost 10 percent due to fears about the European debt crisis and the global economy, but the market is virtually flat so far this year.
Recent data from the Commodity Futures Trading Commission (CFTC) showed speculators sharply cut their copper net shorts after prices rallied more than 5 percent in the week up to July 3, indicating more investors believe that copper prices have bottomed out.
Also, analysts and trade sources in China took the sting out of the poor import data earlier, saying signs have begun to emerge of a pick-up in copper demand there.
Macquarie Commodities Research analyst Bonnie Liu said she was seeing budding signs of improving demand in China, particularly among large copper fabricators that were receiving more orders for state grid construction.
"I think Chinese demand has bottomed out and has started to improve since May, led by government infrastructure spending. The price outlook is comfortable for the second half from recent lows seen in June," she said.
In aluminium, UBS cut its average LME three-month price forecast for 2012 to 98 cents a lb ($2,161 a tonne) from a previous forecast of 101 cents after producers failed to cut capacity as much as expected.
"Without these cuts, the aluminium price will most likely continue to slide," analyst Julien Garran said in a note, adding that the price was expected to average 95 cents a lb ($2,095/tonne) in the third quarter.
Top aluminium maker Alcoa Inc's quarterly revenue and profit beat Wall Street's expectations, even though prices for its aluminium are at nearly two-year lows, and it forecast growing demand in the aerospace and auto sectors.
Zinc fell 1.29 percent to close at $1,830 a tonne, tin rose 0.40 percent to end at $18,775 a tonne, and lead edged down 0.19 percent to close at $1,874.50 a tonne.
In industry news, Hunan Nonferrous Metals Corp Lts , China's top zinc producer, said on Tuesday that it expected to record a loss in net profit for the first half of 2012 as the selling price of its major products fell.
