Renewed fund buying drove London Metal Exchange (LME) prices higher by Wednesday's kerb close with copper eyeing multi-year highs, analysts and traders said.
"It's those famous funds again. They are back and there is no sign of them letting go," one trader said.
"You can't stop it. The money is coming out of the woodwork," a second trader said.
"Every fund and his uncle are buying. Copper is looking at the March peak of $3,055 and in the run up to LME week I reckon it could boil over, however there is a lot of room for a move down now," he added.
Copper jumped to $3,035 a tonne by the close, up from $2,979 on Tuesday.
Sentiment towards aluminium and lead was also positive with the former hitting a nine-year high and the latter a contract peak during the afternoon.
Analysts were concerned that the failure to break above $3,055 could indicate the formation of a triple top.
In a report Roy Carson at brokerage Triland Metals said that a triple top formation at $3,055 needed to be negated, and he was looking for a close above $3,060 in the near term.
Cash/threes backwardation was around $150, easing slightly from an earlier $162.50, its highest since April when the spread reached $185 backwardation.
Aluminium rallied $27 to $1,860. It peaked at $1,870 earlier, scoring to its highest since August 1995.
"There just seems to be a global buying operation, copper, aluminium, lead - the funds will buy anything," the second trader said.
Lead ended $23 higher at $948, just $2 short of the contract high of $950 it reached in the midseason.
Zinc gained $28 to $1,150. Nickel rose $380 to $15,980 a tonne, while tin gained $25 to $9,075.