Since many commodities ETFs don't own the physical commodities, but instead futures or options on them, their tax treatment is quite different compared to a stock or bond ETF. Gains and losses in commodity ETFs that use futures contracts are taxed as 60% long-term and 40% short-term. This creates a blended tax rate ceiling of 23% for investors in the highest tax bracket.
As we've mentioned before, the ideal place for commodity ETFs is inside a tax sheltered account like an IRA, ROTH IRA, or 401(k) plan. Simply put, they aren't very tax efficient held elsewhere.