Most recently the game called "Copper Futures" became very popular:
As the chart shows, now the open interest in copper futures stands at its historic high of 296 thousand contracts.
What is more, the copper trade is not only overcrowded but I see excessive optimism among speculators as well:
Money Managers (in other words, big speculators) are holding the largest long positions in copper futures in history.
Summarizing - the copper market does not look attractive for the buyers now.