There’s more than one way to invest in copper. In addition to buying shares of copper stocks, investors can gain exposure to the red metal through a copper ETF or ETN. For the uninitiated, exchange-traded funds (ETFs) are securities that trade like stocks on an exchange, but track an index, commodity, bonds or a basket of assets like an index fund. In the case of base metal copper, an ETF can track specific groups of copper-focused companies, as well as copper futures contracts or even physical copper. Exchange-traded notes (ETNs) are similar to ETFs in that they track an underlying asset and trade like stocks on an ... (full story)