The light meter in our camera measures the intensity (brightness) of light. Nothing more, nothing less.
This measurement of light is expressed as an exposure. An exposure is expressed in terms of a combination of aperture, shutter speed and ISO.
If we are working our camera in an auto-exposure mode, our camera picks an exposure for us and our composition, in terms of exposure, is limited by the camera.
If we are working our camera in manual-exposure mode, WE pick an exposure and our composition, in terms of exposure, is limited by our imagination.