Your camera meter does one thing and it does it well. It tells you the settings to make whatever you pointed it at 18% gray. The best way to describe how this works is if you have a room that has one white wall and one black wall. If both are lit with the same amount of light and you shoot both of them the pictures will be the same. They will be both gray. The meter will underexpose the white wall and overexpose the black wall. So keep this in mind when you are shooting in obscure situations like snow.