Calling it “metal SLS” is a small lie we all tell. True selective laser sintering fuses polymer powder below its melting point. When the powder is metal, the laser doesn’t sinter, it fully melts, and the process is more honestly called Selective Laser Melting or Direct Metal Laser Sintering, both branches of Laser Powder Bed Fusion (L-PBF). The premise is deceptively simple. A recoater blade spreads a layer of gas-atomized metal powder, typically spherical particles 15 to 45 microns across, just 20 to 60 microns thick. A fiber laser, usually 200 to 500 watts, traces the cross section, creating a molten pool that fuses to the solidified layer beneath. The platform drops one layer. Repeat ten thousand times. What makes it brutal is the physics inside that melt pool: • Cooling rates reach 10^6 K per second, freezing in ultra-fine grain structures impossible to achieve by casting • Marangoni convection driven by surface tension gradients stirs the pool, governing penetration depth • ...