Is it ok to wear mostly black to a wedding?

It is ok to wear mostly black to a wedding? I have a black & white summer skirt, and would prefer to wear a black top rather than a white one as its more flattering on my large frame. I seem to remember hearing somewhere that it is not good etiquette to wear mostly black to a wedding, but with my large size (16-18) I just look enormous in summer colours like pastels/white.