Not true...the amount of light drawn in is according to your aperture.
Whether prime or zoom is the same...prime lens glass doesn't have any special magnetic energy to 'draw in more light'. its not true at all.
Perhaps your conversation with whoever, was referring to a particular fast aperture prime lens? Anyway, most primes have rather fast apertures.
For example, if your kit lens is a 18-135 f/3.5 to 5.6, then your aperture at wide-open while looking through viewfinder is only f/3.5, therefore its not as bright.
Compared to say a 50/1.4, the f/1.4 lens will be brighter on the viewfinder.
However, all these have no effect on your metering, your metering will still be accurate, because the camera can read your lens' aperture position and know what aperture its reading is based on.
This also explains why, for example, when using older lenses which can't have their aperture position "read" by the camera, the camera's metering will not work, as it has nothing to base its metering on. (eg. pre-AIS lenses for Nikons can't meter, for that reason).
