If you are shooting in "manual" mode (and only in manual mode) then the arrow pointing right (off the right edge of the metering indicator) means the camear believes you are going to over-expose the shot.
If you are shooting in a semi-auto mode such as Av, Tv, or P, then the meter indicates the amount of exposure compensation that you've dialed in. The large rear-dial on the camera controls exposure compensation. Half-press the shuttter to start the metering system, then roll the rear-dial counter-clockwise to re-center the arrow on the meter. This control allows you tell the camera that you'd like to exposure for a higher (or lower) amount of light than what the camera meters. E.g. if shooing a white snowy scene the camera will tend to underexpose because of the dominance of white. If shooting dark scenes the camera will tend to over-expose because of the dominance of black. The meter normally believes a shot should "average" out to a "middle gray" value. So when your scene does not truely represent a "middle" gray value then you'd want to compensate using this control.
In manual mode, the arrow simply tells you if it believes you are going to over-expose or underexpose the shot.
If you test the metering on a day in FULL mid-day sun (no shadows, no clouds), set the camera to Manual (it must be on Manual or this wont work) and set the exposure settings to ISO 100, f/16, and 1/100th sec. and set the metering to use evaluative metering then your in-camera meter should show the arrow at or very near the center (particularly if you are metering a scene that should come up with something close to a middle-gray exposure - don't try to metering anything "white" or "black" as this will throw it off.)
Tim Campbell
5D III, 5D IV, 60Da
