The feedback model of on-chip interconnect metal heating during electrostatic discharge (ESD) is extended to capture and simplify overall behavior of the metal. Of greatest interest to risk assessment is the peak temperature Tmax reached during an ESD event, and it is discovered that Tmax for Human Body and Charged Device Model (HBM, CDM) events follows its own simplified feedback equation with constant parameters. These constants are a function of the electrical and thermal properties of the metal layer. The result is a simple relation between Tmax and current density for the HBM or CDM event under consideration, a valuable aid to risk assessment and design rule checks. The summary equations capture the results of many detailed finite element and numerical convolution calculations of heat flow for on-chip metal.