Coupling computer resources to work on a given problem has been a successful strategy for years. Due to the existence of high bandwidth WAN it has become possible to couple big machines to build clusters that outperform the most powerful existing single computers. The article discusses such a powerful cluster, a metacomputer. While for MPPs the message passing model was standardized already 4 years ago (1995), a standard for interoperable MPI has only been published recently. We briefly present an approach for MPI based metacomputing called PACX-MPI. We also describe other approaches, and give an overview of the technical concept.