Exchange-traded funds offer a convenient way to invest in sectors or niches that interest you. If you expect the copper industry to prosper as the global economy gets its legs back and construction and infrastructure projects proliferate, the First Trust ISE Global Copper Index ETF (NYSE: CU) could save you a lot of trouble. Instead of trying to figure out which companies will perform best, you can use this ETF to invest in a lot of them simultaneously.

The basics
ETFs often sport lower expense ratios than their mutual fund cousins. The copper ETF's expense ratio -- its annual fee -- is 0.70%. That's a good bit higher than that of many ETFs, but far lower than that of the typical stock mutual fund. Note that the fund is small, so if you're thinking of buying, beware of occasionally large spreads between its bid and ask prices. Consider using a limit order if you want to buy in.

This ETF is too young to have enough of a track record to assess. Even so, as with most investments, we can't expect outstanding performances in every quarter or year. Investors with conviction need to wait for their holdings to deliver.

What's in it?
Many major copper companies posted poor performances over the past year, but they could see their fortunes change in the coming years.

Southern Copper (NYSE: SCCO), down 9%, has been labeled a stock "on the road to greatness" by my colleague Rich Duprey. It does carry more debt than many of its peers, but it's also planning to boost its production, and it may be able to generate a lot of revenue in copper-hungry China.

Freeport-McMoRan Copper & Gold (NYSE: FCX), down 30%, recently generated about 5% of its revenue from China, and as the country grows that number is likely to rise. The company's recent 67% dividend hike speaks volumes about management's confidence in its future. The company enjoys a very low cost of production, and is expanding all over the globe.

Then there are Rio Tinto (NYSE: RIO) and Ivanhoe Mines (NYSE: IVN), down 24% and 61%, respectively. Ivanhoe is 51% owned by Rio Tinto, and bulls are excited about the Mongolian Oyu Tolgoi copper, gold, and silver project, which is being developed and may contain an eye-popping $300 billion in copper and gold.

The big picture
Demand for copper isn't going away anytime soon. A well-chosen ETF can grant you instant diversification across any industry or group of companies -- and make investing in and profiting from it that much easier.

If you're more interested in gold than copper, check out our special free report, "The Tiny Gold Stock Digging Up Massive Profits," for a compelling candidate for your portfolio.