The metal probably helps to speed up the reaction rate a/c to collision theory, reactant molecules must collide with a reasonable direction by either weakening bonds in reactant molecules to make them extra reactive or by attaching reactant molecules in the exact direction to react.
This is known as an example of heterogeneous catalysis because the catalyst is solid and the reactants are liquid or gases mixture. In this catalysis, the catalyst is present in a different phase compare to the reactants.
