Functionally　graded　metallic　materials　(FGMMs)　are　a　new　type　of　heterogeneous　materials　composed　of　polymetallic　components　with　gradients　in　structure　or　composition.　Compared　with　conventional　homogeneous　materials,　FGMMs　are　able　to　integrate　multiple　distinctive　components　in　a　spatially　controllable　manner,　thereby　creating　a　combination　of　various　advanced　properties　that　are　in　theory　impossible　to　be　simultaneously　possessed　by　a　single　material.　As　a　result,　FGMMs　are　highly　demanded　in　complex　and　harsh　working　environments　such　as　aero　engines　(extreme　temperature　&　pressure),　water　reactors　in　nuclear　power　plants　(high　pressure　&　corrosive),　and　space　stations　(low　pressure/temperature　&　ion　bombardment).　Despite　of　the　great　advantages,　the　preparation　of　FGMMs　by　powder　metallurgy,　centrifugal　casting　and　other　conventional　techniques　can　be　very　challenging,　as　those　methods　lack　the　ability　to　precisely　tune　the　composition　and　structure　of　materials　in　3D　space.　As　an　advanced　manufacturing　technology,　additive　manufacturing　(AM)　features　rapid　prototyping,　high　utilization　rate　of　raw　materials,　and　a　great　shaping　capability,　which　opens　up　huge　opportunities　for　the　preparation　and　development　of　FGMMs.　As　of　today,　the　fabrication　of　libraries　of　FGMM　products　including　bone　plates,　engine　parts　and　the　shield　of　spacecraft　has　been　enabled　by　two　major　AM　approaches,　namely　directed　energy　deposition　and　powder　bed　fusion.　This　article　reviews　the　most　recent　progresses　on　the　additive　manufacturing　of　FGMMs　by　introducing　the　classification　and　design　methods　of　FGMMs,　detailing　the　mainstream　AM　technologies　for　FGMMs,　and　discussing　potential　applications　of　various　FGMMs.　Insights　on　the　challenges　and　future　research　directions　for　the　preparation　of　FGMMs　by　AM　technologies　are　also　presented.　By　bridging　scientific　principles,　AM　technologies　and　material　properties,　this　article　provides　not　only　a　guideline　on　how　to　obtain　desired　FGMMs　in　a　demand-oriented　fashion,　but　also　a　perspective　of　the　potential　evolution　in　this　area.　The　content　will　be　found　helpful　for　general　readers　who　want　to　learn　about　FGMMs　and　researchers　in　this　field　to　prepare　for　their　future　research.　©　2023　Elsevier　B.V.