This document introduces various metric units of measurement including millimeters, centimeters, meters, and kilometers. It explains that millimeters are used to measure very small objects, centimeters are used to measure objects like pencils, meters are used to measure larger objects like rooms, and kilometers are used to measure long distances like the distance between cities. The document provides examples of measuring various everyday objects using centimeters and meters, and explains how to convert between units, such as 100 centimeters equals 1 meter or 1000 meters equals 1 kilometer.