The metric unit that measures the volume of an object with straight sides is the cubic meter (m³) .

Here's why:

* Volume is the amount of space an object occupies.

* Cubic units are used to measure volume because they represent three dimensions (length, width, and height).

* Meters are a standard unit of length in the metric system.

So, a cubic meter is a cube with sides that are each one meter long. This unit is commonly used to measure the volume of larger objects like rooms, buildings, or containers.

For smaller objects, you might use cubic centimeters (cm³) or cubic millimeters (mm³) .