There are many new appearances in SolidWorks 2013, including liquids, plastics, and organic materials such as waxes and translucent marbles. In addition, brushed metals now show directionally-dependent (anisotropic) reflections to create a more realistic appearance.
It is recommended that you experiment with the new materials in a number of different contexts to get the best results. Factors like lighting, reflections, and the thickness of the model affect the appearance.