Almost everyone has heard of the London Stock Exchange, but relatively few know anything about the London Metal and Commodity Exchanges - yet these markets have a greater influence on world economies because they set global prices for some of the essential raw materials for industry and food manufacture. The LME provides three basic services to the world's non-ferrous metal trade. First, it is a market where large or small quantities of metal of a guaranteed minimum standard can be bought and sold on specific trading days. Second, it acts as a barometer of world metal prices. And third, it is a "hedging" medium: that is, it can help traders get some protection from price fluctuations that occur for economic, political or financial reasons.