The standard unit of weight in the metric system is the kilogram (kg). It is defined as the mass of a specific physical prototype stored at the International Bureau of Weights and Measures. The kilogram is part of the International System of Units (SI), which provides a consistent framework for measurement worldwide. It is widely used in science, industry, and everyday applications for weighing various objects and substances. The metric system, including the kilogram, is designed to be user-friendly and easily scalable, facilitating global trade, scientific research, and international communication in quantifying weight and mass.