Despite tremendous advances over the last few decades, experimental measurements of mechanical property degradation in irradiated metals typically provide information integrated over space and time, where the fine details of the microstructure are often lost. Computational modeling and simulation grounded on solid theoretical principles that link physical phenomena across several scales can be used to interpret the experimental data and provide a more complete picture of damage processes. In this talk, we will present two examples of cases relevant to fusion energy where modeling can explain macroscopic measurements of damage in structural materials subjected to neutron irradiation. First, we will show simulations of dislocation channel formation in irradiated ferritic systems, linking nonlinear dislocation mobilities with damage accumulation models, elasticity, deformation models, and experimental data. Second, we will show how the effect of transmutation in tungsten structural materials has a large influence on microstructural evolution and hardening, and how modeling can help bridge the gap between experimental observations and measurements of hardening.