I would use a yardstick, a foot ruler, a tape measure, a meter stick, or a laser rangefinder
to make the measurement.
After I knew the distance, I could convert it into any convenient unit in order to describe it
or report it to others. The most convenient metric units would be either meters or centimeters.
meeters?
millimeters are a measure of distance cubic centimeters are a measure of volume the only similarity is that both are metric
Metres; centimetres are too small, kilometres are too large.
The question is too vague for a proper answer. Distance can crop up in the context of speed, acceleration, kinetics, etc. In each case the definition and formula may vary. There is also the concept of distance between two points in a metric space and the measure of distance will depend on the metric defined on the space. The Euclidean (or Pythagorean) metric and the Minkovsky (or taxicab) metric are two of the more common metrics but there are loads more.
I would assume that you would use cm or even mm if you wanted to be more accurate
Kilometers
The meter.
The metric unit of the meter would be the appropriate measure of the area of classroom. Calculating area involves multiplying the length (in meters) of the classroom's length and width. Area of the classroom would be in square (^2) meters.
Meters
meeters?
The metric system is used to measure distance in Brazil.
millimeters are a measure of distance cubic centimeters are a measure of volume the only similarity is that both are metric
distance
Miles.
Distance is measured metrically in meters
A global positioning system (GPS)
The word, metric, means referring to a measure: it is a measure of some characteristic and how it is measured depends on the way in which it is defined. This may be illustrated by considering the metric for distance. Conventionally, the metric for the distance between two points is the length of the straight line joining them. However, on the surface of a sphere, for example, it is a length along the "Great Circle". In a Minkovski space (for example a road grid like in Manhattan) it is the North-South distance plus the East-West distance.