Methods for forming a seal in a wellbore. An example method includes positioning an expandable metal sealing element in the wellbore; wherein the expandable metal sealing element comprises a composite material of expandable metal and a reinforcement material. The expandable metal forms a matrix and the reinforcement material is distributed within the matrix. The method further includes contacting the expandable metal sealing element with a fluid that reacts with the expandable metal to produce a reaction product having a volume greater than the expandable metal.