It is important to remember that, unlike their name may imply, metal dentures are not made with a cold and unsightly material but with medically approved cobalt chrome metal alloy. Or in some cases a hybrid of cobalt chrome and nylon resin. They are particularly beneficial to people with allergies; the hypo-allergenic material in chrome / metal dentures can significantly reduce the chance of an allergic reaction.
Where used for partial dentures, they are normally stabilised by means of clasps and tooth rests. They help to prevent the denture moving whilst you eat and talk, and any subsequent irritation that this may cause.