Don't do that! NASA lost already 2 and the guys in the shuttle would like to keep control.
In Manual mode: if the pointer / needle is on '0' the camera reads correct exposure with the selected metering mode. Keep the metering mode in mind, read up more in your manual. If the pointer goes off to left or right that means that the exposure will be over or under - again: based on the selected metering mode.
Try for yourself: Mount the cam on a tripod, select a subject with patches of varying brightness. Adjust the cam in Manual mode to show '0' for exposure, then change the metering mode. Watch the result on the exposure meter.