the liter
A millilitre.
The meter is the metric base unit for volume, and the cubic meter is the derived unit.
The standard liquid for measuring volume in the metric system is water.
If, by 'metric system', you mean the 'SI system', then there is no base unit for volume. The unit for volume is called a 'derived unit', and it is the cubic metre (m3).
Common units for measuring volume in the metric system are milliliters (mL) and liters (L). The tool commonly used for measuring liquid volumes in the metric system is a graduated cylinder.
The base unit for measuring mass is kilograms.
Liters & milliliters
This would be measured in cubic meters.
A cubic centimetre (cm3) is a unit of volume (V).
Base units need not have ANY volume. A second is the base unit for measuring time and it has no volume!
Kilograms
In the SI system, the base unit for temperature is the kevin.