Description Metamod:Source is an API manager and interception handler that sits in between the Half-Life 2 Engine (Source) and a subsequent Game Modification (MOD). It can dynamically load "SourceMM Plugins", written in C++, to intercept, override, and hook EngiMetamod:Source is an API manager and interception handler that sits in between the Half-Life 2 Engine (Source) and a subsequent Game Modification (MOD).