I've just been playing with the D700 and metering, as it's a bit different from the Canon. All using matrix metering, in aperture priority mode.
With a white shirt filling the frame I need EC+1. With a black shirt filling the frame I need EC-3. With a white shirt with a black pattern I need EC+1 or close to it. A pink patterned shirt needs almost the same as white, EC+1 or slightly less.
With the frame half white shirt, half black shirt I need EC0, or maybe -2/3. Too close to call. If the black shirt takes 2/3 of the frame and the white 1/3 then I need the same EC, -2/3 or so. If the white shirt fills 2/3 the frame and the black 2/3 I need the same EC as if the black shirt wasn't there, +1.
I guess I need a conclusion or a general rule to go by. It seems that in general it exposes for the highlights, and you need 0-1 EC is there's anything white in the frame. Since most brides wear white, and that's what I shoot, that's pretty much what i'll need.
Next I need to work out how this interacts with flash, also keeping in mind EC and FEC both affect flash exposure, even in manual mode. I also need to look at what happens when the couple don't fill the frame.
Of course I work in manual a lot, so this is really just for interest.