Investing in commodities, by which, it is normally meant the raw materials for industry such as minerals mined, metals refined or agricultural produce, presents a number of practical obstacles.  Private investors can hardly take delivery of several tons of wheat, for example.  

Traditionally, institutions have made money from the commodities markets by trading in forward contracts, futures and options.  These markets are notoriously difficult territory for smaller investors and not generally appropriate for a long term strategy of buy and hold.

So why the interest in commodities?  Well, they can provide the opportunity of an uncorrelated return to add to an investment portfolio, i.e., they do not go up and down at the same time as equity markets much of the time.  Diversification is central to portfolio construction and the search is always on for assets which increase this.  However, as everyone rushes to diversify, assets can start to become correlated.  That said, there is still a case for the inclusion of commodities, even though they have no income generating prospects, important to many investors.

Most will obtain some interest in the commodity markets by investing in companies which derive their earnings from producing them, mining stocks, etc.  Now, however, there are increasing numbers of Exchange Traded Funds (marketed as Exchange Traded Commodities, ETCs) linked to commodities indices.  These give the opportunity to access returns on a broad range of commodities from platinum to oil to livestock and are worthy of consideration for inclusion in a well diversified portfolio for the long haul.