The study investigates the structural, magnetic, electronic, optical and thermoelectric properties of MST (half-semi metallic) compound under strain engineering. Experimentally, MST is metallic nature with zero gap, low thermal conductivity, and minute thermoelectric efficiency (ZT 0.01 at 300K). By applying biaxial strain (tensile and compressive), the gap increased, showing a shift from -4% to +15% with SCF and -3% to +10% with GGA and GGA + TB-mBJ methods. At 4% tensile strain, MST exhibited half-semi metallic behavior with a significant gap (1.24 eV) at a high-symmetry point. Hybrid + SOC calculations showed enhanced thermoelectric performance, with ZT reaching 0.716 for p-type and 0.723 for n-type, suggesting MST potential for thermoelectric applications.