Many people believe that flash is there to be used only when it’s dark but that’s not the case. When we shoot weddings on sunny days we use “fill flash” an awful lot to light areas of deep shadow. Things like ladies hats always cause problems, if you don’t use a bit of fill flash you will get a darkly shadowed area where a face should be.
Very bright sunlight also casts stark shadows under eyes, noses, chins etc so a bit of flash will help to light these areas too
hope you find this of interest