An electronic device may be provided with electrical components mounted in an electronic device housing. A display module may be attached to a display cover layer with a layer of adhesive to form a display module assembly. The display module assembly may include a display module assembly chassis. The display module assembly chassis may include a plastic display module assembly chassis molded over a metal display module assembly chassis. The display module assembly and a backlight unit may be assembled to form a display module that is installed within the electronic device housing or display module assembly layers and backlight unit structures may be assembled into the electronic device housing. The backlight unit may include a backlight unit chassis. A metal housing midplate may serve as part of the backlight unit chassis.