that represent the mechanical response of metallic materials calibrated with experimental tests. Most commonly, these calibrations rely on tensile tests using polycrystalline materials and optimization algorithms that estimate multiple coefficients simultaneously. However, these approaches can result in spurious estimation and large parameter uncertainty for models with large number of coefficients. This talk will discuss sources of uncertainty in plasticity models and will present different examples of epistemic uncertainty affecting the estimation of parameters. We will discuss the use of physics-based approaches to estimate coefficient uncertainty both from models and experiments. We will conclude by examining opening challenges and opportunities to advance the prediction of plastic responses in metals.