Leading base metals rose again on Monday as Asian traders rejoined the investment-led commodities boom after a week-long holiday for Chinese New Year.
"Over the Lunar New Year period the LME (copper) rose above $5,000, so from the Chinese point of view they had to close the gap and so Shanghai copper rose," said Wang Zheng, a metals analyst at Shanghai Dalu Futures.
Last week an influx of fresh investment fund money at the start of a fresh month swirled through the London Metal Exchange (LME), the world's largest non-ferrous metals market.
Copper, used widely from construction to electronics, hit another all-time high of $5,070 before ending $40 higher at $5,060.
Zinc, which is used to galvanise steel to protect it from corrosion, sped to a fresh all-time high of $2,420 on Monday, then settled at $2,400. Aluminium, used in consumer white goods, reached a new 17-1/2 year peak of $2,670, closing $36 higher at $2,669.
"Overall the trend and momentum in most of the metals is up, so until something changes sentiment or until the sellers emerge in force, the path of least resistance is up, even if a vacuum is developing in its wake," analyst William Adams of BaseMetals.Com said.
Investment fund sources say many of the latest investors to join the commodity market boom - pension, endowment and mutual funds - are new to the market.
They are typically investing in indices, driving higher other commodities such as precious metals and oil. Gold hovered near its highest in 25 years on Monday as tensions over Iran's nuclear ambitions mounted, while platinum also firmed on fund buying in Japan and was near all-time highs. But in the midst of a rally that has run for more than two years, worries persist about a potentially sharp reversal.
"These technical trades have been skipping over big price points, so there's a danger that they'll equally lope downhill," said Andrew Harrington, an industry analyst at ANZ Bank.
Analyst Robin Bhar of UBS said that a correction would be welcome, as it would confirm at what level physical buying would emerge. For months, end-users have been holding off from buying more than what is immediately needed.
"Additionally, of course, it will see a shakeout of the weaker longs and provide a better platform from which higher price levels can be sustained," Bhar added.
In the short term, however, many expected copper prices to continue to rise - $5,100 is the next significant target. "The higher the current upswing in prices takes copper, then the more significant this correction will be, although any downward adjustment is still expected to leave copper at a historically high level," John Meyer of Numis Securities said.