The difference is that an Imperial gallon exists,
whereas a 'metric' gallon doesn't.
cc
The metric unit of volume is in liters and milliliters
Graduated cylinder
measure of length...metres measure of weight...kilograms measure of volume...litres
Volume is measured in Liters in the metric system. 1 liter=1000 cubic centimeters (cm3)=1000 mL
The metric 'kilometer' is typically used to express the length of the same category of measurements as the English 'mile'. But it's a stretch to say that they are "about the same". One kilometer is almost 38% shorter than a mile.
The Metric System has evolved over time however it is based on "the mètre des archives" and "the kilogramme des archives" introduced by France in 1799.The accuracy has been improved and extra units have been added to the original system.
Napoleon created Code Civil des Francais, better known as the Napoleonic Code. Some of the French codes today are still based on the Napoleonic Code. Napoleon gave a lot of poor people jobs during his reign. Napoleon had people build the Arc de Triomphe and other beautiful monuments in Paris. He was a genius in the operational art of war. He introduced the Mertic system. Napoleon also emanicipated Jews. So yes, his life was significant.