The movement of a mechanical or quartz watch can be disrupted if it comes near a strong magnetic field. Magnetism is common in a wide variety of electronic products, automobiles, and kitchen utilities, such as refrigerators.
Most Swiss watches claim to be anti-magnetic, which is achieved by using alloys for certain parts, such as the balance wheel and escape wheel. These alloys include Invar (iron, nickel, carbon, chromium alloy), Glucydur (beryllium, bronze alloy), and Nivarox (iron, nickel, chromium, titanium).
Electronic watches are not susceptible to magnetism.