Current research in alkene metathesis has two significant strands of development. One pertains to rapid progress in catalyst development which permits far greater tolerance of organic functional groups. This includes synthesis of new, structurally defined, catalytically active molecules, some of them even performing in aqueous environment. The second aspect is a consequence of the first one. Not only polyfunctional polymeric materials are obtainable as a result of living ring-opening metathetic polymerisation of structurally complex monomers, but alkene metathesis provided an efficient ring-closing strategy for use in synthesizing intricate structural patterns of important organic molecules. In this review, the information is classified in terms of type of catalysis -- homogeneous or heterogeneous. Each type is subdivided according to the metal used, so that a reactivity pattern might emerge to guide future developments.