The answer would depend on what characteristic of the drop of water you wished to measure: its mass, surface area, volume, length, shape, refractive index, and so on. In any case, the tool would be much the same as the tool used for the traditional measurement - only the units would differ/
Drop it in the water.
(the metric unit) The average bacteria is only about a micrometer in length, so there may be thousands in a single drop of water. (the tool) He used a micrometer to measure the thickness of the circuit board.
You can use the blending tool. (which look like a water drop) It is located with your brush, lasso tool, eraser, crop tool, etc. in that box or bar. You could also use the smudge tool. (which is in the same place as the blending tool. Left lick on the little arrow in the corner of the blend tool and then choose the smudge tool on the drop down menu). You could also use the gradient tool. (I'm referring to Elements 5, so it may be where the bucket tool is [again, choose the drop down arrow and then select] or it may have its own icon. It will be a square that is lighter on one side and darker on the other.)
No
A ruler
There are no tools that are specific to metric system: the same tool can also be used for the Imperial system. The best metric unit of weight of a CD is probably the millinewton.
measuring tape
Tool:meterstisk
Heat. The water will evaporate and leave the sugar behind.
kilometer/ odometer
Grams. Obviously.
No a meterstick is a tool used for measuring..mass, volume, time, length, and temperature are all metric units