You will have to install metric Libraries and Template files and reset the default paths to point to those metric. Once Revit's default project and family template paths are changed you will have a metric versus imperial environment. Technically imperial and metric setup has nothing to do with the project or family editor, but the template and library files Revit uses to setup a project or family.
Mel Persin, AIA
AEC Technology Consultant
Technology to Visualize and Realize Solutions
Modeling for the Future/Drafting in the Present/Building on the Past