The　study　examines　the　structural,　electronic,　optical,　mechanical　and　thermal　properties　of　halide　perovskites　A(3)MCl(3)　(A　=　Mg,　Ca;　M　=　N,　Bi)　using　Density　Functional　Theory　(DFT).　The　structure　was　optimized　using　the　Generalized　Gradient　Approximation　-　Perdew-Burke-Ernzerhof　(GGA-PBE)　method,　while　the　electronic　and　optical　properties　were　calculated　using　the　HSE06　hybrid　method.　The　electronic　properties　indicate　that　Mg3NF3　exhibits　a　wide　band　gap　and　behaves　as　an　insulator,　while　Ca3BiCl3　and　Mg3BiCl3　display　semiconducting　behavior.　According　to　electronic　band　structure　simulations,　Mg3NF3　act　as　insulators,　while　Mg3BiCl3　and　Ca3BiCl3　exhibits　semiconductor　behavior.　Studies　of　optical　properties　demonstrate　that　compounds　with　Bi　absorb　strongly　within　the　UV-visible　range　and　reflect　very　little　throughout　the　spectrum.　The　compounds　show　brittle　behavior.　Mg3NF3　being　the　stiffest　and　having　the　lowest　level　of　anisotropy　with　wide　band　gap　insulator.　According　to　thermal　analysis,　Mg3NF3　melts　at　a　high　temperature　and　is　a　good　thermal　conductor,　which　showed　promising　for　applied　as　heat　sink　materials.　Mg3BiCl3　and　Ca3BiCl3　compounds　showed　low　thermal　conductivity　and　are　therefore　suitable　for　use　in　thermal　barrier　coatings.　The　combined　findings　identify　A(3)MCl(3)　compounds　as　promising　candidates　for　multifunctional　electronic,　optoelectronic,　photovoltaic,　and　thermal　management　devices.