The human-metal-model (HMM) describes the discharge of an electrostatically charged human via a metallic tool and a grounded component. It assumes the discharge to be triggered by contact of any pin of the component with the metallic tool, while any other pin of the same component is grounded. In contrast to other component-level discharge models, "pin" has to be understood only as an especially exposed terminal of the component.
The HMM adapts an ESD model, that was originally standardized in IEC 61000-4-2 on system-level, for components. While the original model is especially important for the manual assembly of assembled printed-circuit-boards (PCB), modules and equipment into electrical systems, its adaptation for components addresses special cases, which occur seldom and have only a limited significance for the ESD robustness of a given system. The HMM is therefore strongly disputed among ESD experts.