The effect of strain on the reactivity of metal surfaces is investigated using self-consistent density functional calculations for O and CO adsorption, and CO dissociation on strained and unstrained Ru(0001) surfaces. The study shows that surface reactivity increases with lattice expansion, accompanied by an up-shift of the metal d states. The results indicate that strain significantly affects the chemical properties of metal surfaces, with implications for catalytic activity. The effect is explained by shifts in the metal d bands induced by stress, allowing the development of a model for the effect that can be extended to other catalytically important systems. The study demonstrates that both molecular (CO) and atomic (O) chemisorption energies, as well as barriers for surface reactions (CO dissociation), vary substantially on strained lattices. The results are consistent with experimental observations and show that the d-band center (εd) is a key parameter determining reactivity. The correlation between interaction strength and εd holds for many different adsorbates and metals, suggesting that surface strain can be used to tailor the catalytic activity of metals. The study was supported by the Danish Research Councils and the Center for Surface Reactivity.The effect of strain on the reactivity of metal surfaces is investigated using self-consistent density functional calculations for O and CO adsorption, and CO dissociation on strained and unstrained Ru(0001) surfaces. The study shows that surface reactivity increases with lattice expansion, accompanied by an up-shift of the metal d states. The results indicate that strain significantly affects the chemical properties of metal surfaces, with implications for catalytic activity. The effect is explained by shifts in the metal d bands induced by stress, allowing the development of a model for the effect that can be extended to other catalytically important systems. The study demonstrates that both molecular (CO) and atomic (O) chemisorption energies, as well as barriers for surface reactions (CO dissociation), vary substantially on strained lattices. The results are consistent with experimental observations and show that the d-band center (εd) is a key parameter determining reactivity. The correlation between interaction strength and εd holds for many different adsorbates and metals, suggesting that surface strain can be used to tailor the catalytic activity of metals. The study was supported by the Danish Research Councils and the Center for Surface Reactivity.