Copper was up 2.3 percent by the close of London trade on Monday, supported by a strike vote at the world's largest copper mine in Chile, while nickel was underpinned by critically low stocks, traders said.
"At the moment the main factor is supply problems...both in nickel, but also in copper," Kevin Norrish, analyst at Barclays Capital, said.
Copper for delivery in three months closed at $7,850 a tonne on the London Metal Exchange (LME) after gaining $200.
Workers at Escondida, the world's largest copper mine, will resume contract talks with owner BHP Billiton, after last week voting in favour of a strike that could start August 7 if talks fail.
"Today was the end of the month, there will have been some window dressing. Too many people need a good close so they can show the month has been profitable," a trader said.
He added that the market had known about the expiration of the Escondida contract and many had anticipated a strike vote.
"People who have not covered against it have not been very clever."
A rockslide at Codelco's Chuquicamata mine, also in Chile, will take weeks to repair as is costing about 960 tonnes per day of lost in production.
"The combination of a strike at Escondida and the production disruption at Codelco are likely to tighten up the copper market considerably," William Adams of Basemetals.com said.
Dealers also were talking about recent US GDP data, indicating a slowdown of economic growth, as negative for the demand of base metals.
"The market is quite nervous and several investors are sitting on their hands while digesting news about strikes and economic growth," another trader said. "Sentiment is bullish with the fundamentals still in place for some of the metals to test new highs," he said.
Stocks in LME warehouses fell 900 tonnes to 97,450, equivalent to around two days of global consumption.
Nickel last traded at $25,450, up from $24,650 on Friday, when it rose 5.3 percent to hit $25,000 and was nearing its record $26,850-peak set earlier in July.
The metal was underpinned after Inco Ltd said it was shutting down its 54,000 tonnes per year Voisey's Bay mine in Canada and critically low stocks, which dropped 144 tonnes to 4,128, their lowest since July 1991.
Global nickel consumption is around 3,500 tonnes per day.
Despite high prices, analysts saw little impact on stainless steel production, which accounts for about 70 percent of global nickel use.
Aluminium was at $2,580 versus $2,525.
Century Aluminium Co said workers at its Ravenswood facility in West Virginia intended to strike and the company was shutting down the plant. In 2005, the company produced around 616,000 tonnes of primary aluminium.