Where is the water control layer in an exterior wall made up of metal studs with exterior sheathing and air /water barrier and exterior ridged insulation containing windows?

The air and water barrier applied to exterior sheathing and taped to window mullion flashing acts as that control layer in this area of the country.

Also an exterior sheathing that has an integral air and water barrier then taped and sealed to the window mullion flashing can also act as that control layer.