In　recent　years,　searching　for　efficient　solutions　to　improve　the　emission　and　performance　characteristics　of　diesel　engines　is　considered　as　one　of　the　essential　and　urgent　work.　Metal　nanoparticles　with　a　large　surface　area　and　high　heat　transfer　coefficient　could　provide　the　impressive　additive　ability　to　the　fuel　reactivity　and　atomization.　Therefore,　the　critical　role　of　metal　nanoparticles　in　the　support　of　diesel　engine　behaviors　using　biodiesel　and　diesel　is　thoroughly　evaluated　in　this　current　review.　Indeed,　preparation　methods　and　critical　properties　of　metal　nanoparticles　and　metal　nanoparticles-laden　fuels　are　fully　introduced.　More　importantly,　the　performance,　combustion,　emission　characteristics,　and　tribology　behaviors　of　diesel　engines　running　on　metal　nanoparticles-laden　biodiesel　are　compared　to　diesel　fuel　in　detail.　Generally,　metal　nanoparticles-included　biodiesel　facilitates　the　formation　of　a　more　homogeneous　oxygen-containing　mixture　of　fuel–air,　resulting　in　a　more　complete　combustion　process　than　that　of　diesel　fuel.　As　a　result,　the　use　of　biodiesel　with　the　presence　of　metal　nanoparticles　is　considered　as　the　potential　strategy　for　promoting　spay　and　atomization,　enhancing　the　combustion　process,　increasing　brake　thermal　efficiency　(BTE),　reducing　toxic　emissions　(including　carbon　monoxide　(CO),　unburnt　hydrocarbon　(HC),　and　smoke),　and　improving　tribology　characteristics.　However,　some　drawbacks　are　also　indicated,　such　as　increased　NOx　emission　and　brake-specific　fuel　consumption.　In　addition,　it　is　also　concluded　that　studies　on　other　environmental　impacts　(such　as　PM　emission),　the　stable　properties　of　metal　nanoparticles,　and　economic　aspects　should　be　made　more　extensively　before　commercial　applications　of　metal　nanoparticles　in　the　real　world.　©　2022　Elsevier　Ltd