Final answer:
The metric equivalent of 0.001 gram is 1 milligram, with milligrams being used to measure very light objects in the metric system.
Step-by-step explanation:
The metric equivalent of 0.001 gram is 1 milligram (mg). This is because a milligram is defined as 1/1000th of a gram. Therefore, there are 1000 milligrams in a single gram. When measuring mass in the metric system, common units include grams, milligrams, and kilograms. For smaller objects, such as a speck of dust, milligrams are the appropriate unit, whereas grams might be used for objects like paperclips, and kilograms for heavier items like kittens or textbooks.