The plausibility factors influencing heterogeneous nucleation at the metal/glass interface were systematically investigated as a function of temperature. Secondary phase formation at the metal/glass interface is governed by the contact angle, which is affected by volumetric changes, microstructural evolution driven by metal ion diffusion, and redox reactions influenced by the arrangement of oxygen layers on the metal surface. A comprehensive model was developed to describe these plausibility factors based on observed interfacial phenomena. Despite the inherent non-uniformity in ion distribution within the glass, the interfacial diffusion coefficient, derived from an Arrhenius plot, exhibited a clear temperature dependence, reflecting thermally activated diffusion processes. Above the glass transition temperature (Tg), chemical interactions between diffusing metal ions and migrating glass constituents were identified as the main driving force for secondary phase formation at the metal/glass interface. These chemical reactions not only alter the local stoichiometry but also contribute to structural rearrangements at the interface. The results highlight the complex interplay between the thermal, chemical, and structural factors that control nucleation at the metal/glass boundary. The proposed model provides valuable insight into the mechanisms of interfacial phase formation and offers a useful framework for the design and processing of metal/glass composite systems with tailored properties.