In metallic glasses, a high Poisson's ratio often corresponds to a large plasticity and ductility. Yet the physics underpinning such a connection is still poorly understood. Here through finite element simulations, we reveal that a high Poisson's ratio could promote the inhomogeneous stress distribution in metallic glasses. The inhomogeneous stress field could cause earlier nucleation and easier arrest of shear bands, and therefore better plasticity. Experimental results also show a trend of decreasing shear limit with Poisson's ratio. These findings suggest that the stress inhomogeneity might be a key to understand the effects of Poisson's ratio and loading condition on the plastic deformation behaviors of metallic glasses.