A head-mounted display device including a display system and a light modulator is provided. The display system is configured to selectively display a first content to be visually recognized as being superimposed on a scenery of a surrounding environment, or not display the first content. The light modulator, positioned between the display system and the surrounding environment, includes an array of pixels, wherein a portion of the pixels is configured to modulate light to present a display of a second content, while the rest of the pixels are configured to be substantially transparent to light.