In most cases, a man wearing a pair of metal eyewear is of grace and intelligence. Still some guys look very handsome with semi rimless metal eyeglasses frame. Perhaps, you can let him try. Of course, you shall consider his face shape and his clothes styles so as to choose the best suitable pair. If he often wear casuals, you can try black full frame plastic eyeglasses or other colored plastic eyeglasses frames. If he often wear suit, you can consider metal frame eyeglasses for him.
Choosing suitable eyeglasses frame shall consider his face shape and skin color. To match him, you'd better choose eyeglasses frame with similar color to his skin tone. Besides, choosing eyeglasses frame with contrast shape to your boy friend's face shape. If you have no idea what eyeglasses to choose, you can use his photo to virtual try on at some online eyeglasses shop so as to help you decided which eyeglasses to choose.
Metal eyewear is more suitable for a man because man wearing metal eyewear looks more elegant and intelligent. Moreover, square plastic frame are also a happy choice. However, it depends on your style and personality.