The kilogram.
The SI unit for mass is the kilogram (kg)
You would typically measure the mass of a snowflake in the metric unit of milligrams (mg), as snowflakes are very small and light objects.
Metric ruler
Kilogram
The gram.
Grams.
The appropriate metric unit to measure the mass of a lawn mower would be kilograms (kg). This unit is commonly used for measuring the weight of objects in metric system.
Pounds.
Not sure what you mean with "light build". The SI (metric) unit for mass is the kilogram. For small objects, smaller units such as grams and milligrams can be used; for larger objects, the ton (= 1000 kilograms) is also used.
The best metric measurement of the mass of a letter would be in grams. This unit of measurement is commonly used to weigh small objects like letters due to its precision and convenience.
I would use grams.
Mass is measured in kilograms. For larger objects, tonnes are sometimes used. 1 ton = 1000 kg.