Description: Sal discusses metric units of mass or weight such as milligram, gram, and kilogram. Created by Sal Khan. Let's think about the units typically used in the metric system to measure an object's weight. And I'm putting the weight in quotation marks right over here because the units I'm going to talk about are units of mass. Now, in everyday life, if we're just on the same planet or the same part of the planet, if something has more mass, it's going to have more weight.*Teacher Advisor is 100% free.