Chemomechanics of solids can be viewed as an extension of classical solid mechanics that accounts for chemical effects arising from the presence of guest species within a host solid. We consider a chemomechanical framework in which the host–guest system is treated as a single enriched continuum, with its kinematic description augmented to incorporate chemical effects. Accordingly, each chemical constituent undergoing compositional changes is described by two independent kinematical fields: a chemical displacement, whose time derivative defines the chemical potential, and the constituent density. The governing equations are formulated within the framework of continuum mechanics by combining standard mechanical force balances with generalized force balances associated with the chemical kinematics, together with a constitutive theory consistent with a mechanical formulation of the second law of thermodynamics. Building on this formulation, the approach is applied to metal-hydrogen systems to examine how chemically induced strain-deformation driven by changes in hydrogen content gives rise to mechanical effects on chemical processes such as hydrogen entry from the environment and hydrogen trapping within the bulk, which are modeled as surface and bulk chemical reactions. Conversely, chemical effects associated with hydrogen diffusion and trapping are shown to alter configurational forces and the J-integral, thereby influencing fracture-driving forces in hydrogen-rich environments. Analytical considerations, complemented by numerical modeling, are used to assess the significance of the coupled effects predicted by the theory and to identify regimes in which these effects may be neglected.