Patterning　complex　metallic　structures　via　additive　manufacturing　(AM)　has　broad　applications　in　energy,　medical　and　aerospace　industries.　Current　AM　methods　are　often　limited　by　high　processing　temperature,　discontinuous　film　deposition　and/or　low　product　conductivity　and　reflectivity.　We　present　a　versatile　room-temperature　metal　printing　technique　based　on　polymer-assisted　photochemical　deposition　(PPD).　Two-dimensional　(2D)　and　three-dimensional　(3D)　printing　of　silver,　gold　and　platinum　structures　with　feature　sizes　as　small　as　5　mu　m　are　demonstrated　on　various　substrates,　including　silicon,　glass,　polymers　and　biocompatible　hydrogels.　The　PPD-printed　metal　films　are　continuous　and　smooth　(roughness　＜3　nm)　even　at　ultra-low　thicknesses　(＜10　nm),　and　highly　conductive　(similar　to　3　x10(5)　S　cm(-1))　and　reflective　comparable　to　that　of　vacuum　deposited　counterparts.　This　breakthrough　in　advanced　AM　technique　holds　great　promise　for　low-cost,　fast　and　distributed　manufacturing　in　optics,　electronics　and　robotics.