The Market Metric affects how rate information is displayed on different pages. Market Low, Market Average, and Market High can be chosen. Each of these metrics provides different types of market comparisons depending on which is chosen. In most cases, when your prices are compared to the market rate, the comparison type used will be the metric that you have chosen.
Additionally, the default contract length to be searched by default can be chosen within the Market Metric menus. For example, by choosing "short term", all searches performed will display rates for short-term contracts by default until a different contract length type is chosen.
These choices will be the default for all rate comparison features unless specified otherwise.
For more information on how these metrics are calculated, visit the article here.