Metric weight units are a system of measurement used to measure mass or weight. The four solutions for the term METRIC WEIGHT UNIT are GRAM, KILO, MOL, CARAT, and TONNE. A GRAM is a unit of mass in the metric system equal to one thousandth of a kilogram. A kilo is a unit of mass in the metric system equal to one thousand grams. A mol is a unit of mass in the metric system equal to one thousandth of a GRAM. A CARAT is a unit of mass in the metric system equal to two hundred milligrams. A tonne is a unit of mass in the metric system equal to one million grams.