If you hold a commodities or metals ETF, it's worth understanding that these funds work differently than a typical stock or bond fund — and those differences affect your returns.
Most commodity ETFs don't hold physical oil or copper. They hold futures contracts — agreements to buy a commodity at a set price on a future date. While the contract is active, its value moves with the market much like a stock does.
The key difference is what happens when the contract expires. The fund sells it and buys a new one with a later date. This is called "rolling." With stocks, you buy and hold. With futures, the fund is constantly cycling into new contracts — and the price of the next one isn't always the same as the last. That price difference, called roll yield, can add to or subtract from your returns over time. It's one reason a commodities fund doesn't always track the commodity price you see in the news.
There's another difference worth knowing. When a fund buys a futures contract, it only puts down a fraction of the total value. The rest of the fund's cash typically sits in short-term Treasury bills, earning interest — so a commodities ETF is generating income on the side that has nothing to do with commodity prices.
Commodities can provide diversification relative to stocks and bonds, and they've historically been sensitive to inflation. Understanding the mechanics underneath is useful context for knowing what this type of holding is actually doing inside your portfolio.
For educational purposes only. Not tax, legal, or investment advice.