Convert imperial units to metric units to gain an idea of how long each metric linear measurement is. Use an online unit conversion calculator to do this. For example, one inch is 2.54 centimeters, one foot is 30.48 centimeters and one meter is 3.24 feet.
Memorize the basic units of metric linear measurement and understand how these units relate to each other. Understand that 10 millimeters make up one centimeter, 100 centimeters make up one meter and 1,000 meters make up one kilometer.
Examine the lines and numbers on a metric tape measure and determine which represent millimeters, centimeters and meters. The 10 short lines between each number represent 10 millimeters, each number that separates the 10 short lines represents centimeters and each number with an "m" place next to it represents meters.
Practice using a metric tape measure to measure long things, short things and very short things to become accustomed to using metric units.