Copper fell on Friday due to a strong dollar buoyed by U.S. economic data, outweighing the positive impact of a surprise move by Japan to expand its stimulus program.
U.S. consumer sentiment in October hit its highest level in more than seven years and U.S. third-quarter wages marked their largest rise in over six years, although consumer spending dipped in September.
"It's the strong dollar and also it's the end of the month," said a London trader, referring to investor activity to adjust portfolios at month-end.
The dollar index hit the highest levels since June 2010, weighing on commodities priced in U.S. currency since it makes them more expensive for buyers outside of the United States.
The dollar rally overwhelmed the positive impact of the Bank of Japan's surprise move to expand its stimulus program, which earlier lifted copper.
Three-month copper on the London Metal Exchange (LME) closed down 0.6 percent at $6,695 a tonne after touching a session high of $6,795.
Despite the daily loss, copper managed a gain of 0.4 percent on the month, its first such rise since July.
The Bank of Japan unexpectedly eased monetary policy on Friday in a 5-4 vote, due to concerns that cheaper oil would weigh on consumer prices and delay a shift in sentiment away from deflation.
The move sparked a rally in global equity markets and pushed the yen to a seven-year low against the dollar.
Cheaper money tends to spur demand for commodities because it lowers the cost of business, and raises the value of hard assets against depreciating fiat currency.
"We saw some significant moves in Asian risk assets and that has lent support to risk appetite and to base metals," said Gayle Berry, metals strategist at Jefferies Bache.
"To me it feels temporary, but that said, positioning is short for some of the metals and the complex could have a bit of a bounce towards the end of the year."
Alleviating some concerns about supply, workers at Freeport-McMoRan Inc's Indonesian copper mine have canceled a planned one-month strike due to start next week, a union official said, after reaching an agreement with management.
"We have a call for a modest downside in the (copper) price to just below $3 a pound ($6,600 a tonne). But too much below that, you see scrap supply drying up and China is pretty price-sensitive at those levels," said analyst Daniel Morgan at UBS in Sydney.
Other metals pared gains but remained in the positive column, including aluminum, which rose 0.7 percent to close at $2,039 a tonne and gained nearly 4 percent in October.
The premium for cash to three-month prices <CMAL0-3> soared as much as $24, its highest in 22 months. A premium for nearby material typically indicates shortages in metal for immediate delivery.
"This is all part and parcel of aluminum spreads becoming much more volatile. There is a risk that if there is enough volatility (in the spreads) we could see some of the aluminum financing deals being unwound," Berry said.
In other metals, LME nickel hit a two-week high of $16,175 a tonne before paring gains to finish the day virtually flat at $15,780, up 0.03 percent or $5.
Zinc closed up 0.3 percent at $2,307 a tonne, lead added 0.2 percent to end at $2,010 while tin tumbled 2 percent to finish at $19,700.
(By Harpreet Bhal and Eric Onstad; Additional reporting by Melanie Burton in Sydney; Editing by Jason Neely)