The excellent performance of metal foams is well-recognized in the thermal and energy fields. This paper presents an investigation on the convective heat transfer and thermal performance of microchannel heat sinks with different structures of metal foams, such as Y-shaped, metal foam attached to fins, combined metal foams. The inlet Reynolds number is ranging from 170 to 554 and the porosity of the metal foam is ranging from 0.7 to 0.9. The detailed thermal performance and flow characteristics are presented and analyzed by using computational fluid dynamics with a verified computational model. The influences of flow velocity and porosity of the metal foam on the flow and heat transfer characteristics in a microchannel are also observed. It is found that different configurations and locations of metal foam in microchannel result in different heat transfer characteristics. The microchannel heat sinks with combined metal foams have better overall thermal performance than the other two models because it possesses the advantages of mixing fluid flow caused by Y-shaped metal foam and contacting the fins closely. Therefore, properly designed configurations of metal foams can further enhance the microchannel heat sink cooling capacity. Besides, the porosities have a small effect on the thermal performance but have a larger effect on the pressure drop. (C) 2017 Elsevier Ltd. All rights reserved.