measuring tape
Weighing balance is used to measure mass. The metric unit is kilograms.
metric ruler
Meters (about 3 feet)
The most appropriate measure is a metre.
You would use the metric unit "meters" to measure the length of a room.
You can use a thermometer to measure room temperature accurately. Place the thermometer in the room for a few minutes to ensure an accurate reading.
A ruler
A tape measure is typically used to measure the length of a room. Simply extend the tape along one wall to the opposite wall to get an accurate measurement.
You can use a measuring tape or a laser measuring device to measure the distance to the door in metric units, such as meters or centimeters. Simply extend the measuring tool from your starting point to the door to determine the distance.
You can use a tape measure, a laser measure, or a yardstick to measure the height of a room. Simply extend the measuring tool from the floor to the ceiling, making sure to account for any obstructions like furniture or molding.
You would use a tool to measure the lengths of the sides or radii of the area and then use a formula to convert the lengths into an area. The tool would depend on the size of the object and the precision required. The tool could be an electron microscope, or a ruler, or a telescope and in general there would be no difference between a tool used to measure in the metric system or the imperial system. As an example of an unusual tool to measure area... in certain types of chemistry, the chemist needs to measure the area under a peak on a graph, and the traditional way of doing that is to cut the peaks out of the graph and weigh it on an analytical balance. Assuming the paper is fairly consistent in terms of density, the ratio of the weights is the same as the ratio of the areas.
The recommended uint in SI is litre (L) or the submultiple mL.