Defective　hexagonal　boron　nitride　nanosheets　(h-BNNSs)　supported　by　Ni(111)　and　Cu(111)　surfaces　have　been　systematically　studied　in　this　work　by　first-principles　methods.　The　calculation　results　show　that　various　defects　play　an　important　role　in　enhancing　the　stability　of　h-BNNS/metal　heterostructure.　Importantly,　significant　electron　transfer　through　the　interface　between　metal　substrate　and　h-BNNS　to　the　defect　sites　can　make　h-BNNS　more　catalytically　active.　Using　the　oxygen　reduction　reaction　(ORR)　as　a　probe,　it　is　shown　that　the　binding　energies　of　O-2*,　OH*,　OOH*,　and　O*　on　h-BNNS/Cu(111)　with　a　boron　vacancy　(V-B)　are　quite　similar　to　those　observed　on　the　Pt(111)　surface,　suggesting　inert　h-BNNS　materials　with　defects　can　be　functionalized　by　metal　surfaces　to　become　catalytically　active　for　the　ORR　process.　On　the　other　hand,　the　reaction　mechanism　of　CO　oxidation　on　Ni(111)　and　Cu(111)　supported　h-BNNS　with　VB　is　systematically　investigated.　The　h-BN/Cu(111)　catalyst　with　a　V-B　precovered　by　a　CO　species　exhibits　catalytic　capacity　for　CO　oxidation　with　a　lower　energy　barrier　compared　with　that　on　h-BN/Cu(111)　without　any　defect.　While　on　Ni(111)　supported　h-BNNS　with　a　N　vacancy,　the　defect　site　turns　to　be　dominated　by　O-2　and　the　energy　barrier　is　significantly　increased,　indicating　its　dependence　on　the　type　of　defect.　This　work　will　provide　information　for　designing　h-BN-based　catalysts　in　heterogeneous　catalysis.