Prices for copper, zinc and other industrial metals are up close to 20 percent this year.

Many investors talk about the stock market's gains this year, but another top-performing asset class was base metals, such as copper, zinc, nickel and other industrial metals.

New York copper futures prices are up about 24 percent, and the PowerShares DB Base Metals Fund (DBB), an exchange-traded fund that tracks copper, zinc and aluminum, has gained 22 percent. The gains come after some hard times for commodities because of oversupply and subdued demand the past few years. But global economic growth is helping industrial metals, and forecasts for worldwide growth in electric vehicles has underpinned other metals like nickel and cobalt.