The polymer thin film with non-linear electrophysical properties was used as detector for phase transition in metals (Wood's alloy and indium). A voltage has been applied to the metal-polymer-metal structure and the current through structure has been measured as function of temperature. Two independent series of experiments were carried out when the polymer film is heated together with the metal and when the metal is heated only. They revealed sharp change in the current through experimental structure at the melting-crystallization point of metals. This effect is related to a change in electrochemical potential when there is a phase transition in the metal and it results in a change of the temperature dependence of current. This method can be successfully used to detect the critical temperature without the need for direct contact of the polymer detector with the test material.