The chemical reactions and pathways involving phosphonates, any organic compounds containing one or more C-PO(OH)2 or C-PO(OR)2 (with R=alkyl, aryl) groups. Metabolism of phosphonic acid itself, an inorganic compound without the biochemically relevant C-P bond, is not included. [ https://www.worldcat.org/search?q=bn%3A0721662544 GOC:js ]