The term ‘heavy metal’ is generally used to refer to a group of metals with densities greater than 5.0 g/cm³. Under this definition, silver, which has a density of 10.49 g/cm³, is indeed a heavy metal – as are iron (7.9 g/cm³), nickel (8.9 g/cm³), copper (8.9 g/cm³) and gold (19.32 g/cm³).
Heavy metals which are particularly resistant to corrosion are known as noble metals. These include gold, silver and platinum group metals.
It is their corrosion resistance and lack of reactivity that makes noble metals suitable for use in jewellery and dental implants.
(Fun fact: artificial joints, catheters and plates for broken bones are coated with silver to inhibit bacterial growth.)