meters
Kilometers
Kilograms
I would use meters
There is only one metric system. The relevant units, within that system would be millimetres.
In the English (or imperial) system, distances are measured in inches, feet, yards, or miles, depending on what kind of distance you want to measure. In the metric system, commonly used units are millimeters, centimeters, meters, kilometers - again, depending on how long the distance is, you would usually choose a shorter or a larger unit.
Meters
inches or centimeters, I would use inches.
Kilometers
distance
What metric unit would you use to measure a computer keyboard
A ruler
Kilograms
This information is already posted at Wikipedia as follows: http://en.wikipedia.org/wiki/Metrication_in_Australia
Litres
It would probably be miles.
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.
A metric ruler.