It is significant to have locally non-uniform designs in the flow fields since distributions of the current density, temperature, gas, and water concentration are usually non-uniform along the flow path in the polymer electrolyte membrane fuel cell. In this study, we introduce and use several different metal foam flow fields with different porosity gradients as flow distributors in the fuel cell. By evaluating and analyzing polarization curve, power curve, and electrochemical impedance spectroscopy test results, we verify that the tailored porosity gradient in the metal foam flow field has positive impacts the performance of the fuel cell. Maximum power density of the fuel cell with proper porosity gradient in the metal foam flow field increased by 8.23% compared with the conventional metal foam flow field without porosity gradient. In conclusion, we not only explain why proper porosity gradient in the metal foam flow field makes the performance of the fuel cell improve, but also investigate the performance enhancement in the system net power aspect. (C) 2020 Elsevier Ltd. All rights reserved.