Copper and zinc ended near fresh record highs on Monday on the London Metal Exchange (LME) as fund interest and lower inventories fuelled buying, analysts said.
"Nothing can stop it," a fund manager said. "The main buyers are new investors like pension funds starting from scratch in commodities, and for them the actual price level is not relevant."
"When they buy they aren't buying copper because it's at $6,000, they are buying baskets of commodities."
Analysts expected prices to remain highly volatile ahead of the Easter holidays this weekend and possibly for some profit-taking to hit after the latest leg up.
"But it is unlikely that anyone will want to go short in this bull market," said Ingrid Sternby, analyst at Barclays Capital.
Nickel was closing in on its long-standing early-2004 high of $17,720. A breach of that level would take prices to their firmest in 17 years.
"Nickel is heading for $18,000 and I don't see why it wouldn't get there before the end of this week", Sternby said.
Copper hit a new high of $5,940 a tonne on the electronic trading system Select and finished the day at $5,910 a tonne, up $185 from Friday.
The red metal has gained some 24 percent over the past month and is up by a third since the end of 2005. Supply interruptions and strikes have highlighted scarce availability, while LME warehouse inventories are being eroded. On Monday, stocks fell 900 to 111,800 tonnes.
A lack of new exploration investment by miners and the greater political risk linked to the location of many new projects were seen as important factors behind the high prices.
Zinc finished at $2,911, up $106. It earlier touched a record peak of $2,927 and is up some 50 percent since the start of the year on tight concentrates supply and growing demand.
Strength in metals prices boosted stocks in mining shares, with the FTSE 100 ending just a few points shy of a fresh high for the year. Miner Antofagasta was one of the top sector gainers, ending up 3.3 percent.
Nickel closed at $17,425, up $575, after touching $17,650, the highest since January 2004.
Labour negotiations at nickel miners Inco and Alcoa are approaching, which were expected to be difficult, adding considerable risk to supply and were likely to support price levels, analysts said.
Aluminium ended at $2,574 against $2,540, aided by a 7,575-tonne stock fall. Lead closed at $1,182/1,184, up from $1,154 and tin finished at $8,600/8,625 against $8,430.