Per their prospectuses, they must purchase the commodities, and for these funds, this means buying the futures contracts.

FORBES: Commodity Bubble Redux In Full Effect

To achieve and sustain universal access to health care, governments must be able to purchase sufficient and regular supplies of commodities at affordable prices.

FORBES: Connect

This ETF gives access to the Chinese materials and commodities sector that would benefit from increased home building and the purchase of consumer appliances and furniture associated with it.

FORBES: How To Trade On Rising Chinese Inflation

Commodities are typically priced in dollars and a decline in the currency allows overseas buyers to purchase materials at lower prices.

NPR: Dow Jones Average Closes At Another Record High