Metallic microneedles are attractive for painless transdermal drug-delivery. However, fabrication techniques for metal microneedles are often complex and multi-step. In this study, a scalable manufacturing of metallic microneedle arrays is presented using thermoplastic drawing of metallic glasses. Microneedles with tunable lengths and tips are produced by controlling the rheology and fracture of metallic glass. The same drawing process can generate solid and hollow microneedles simply by varying the thickness of metallic glass. The mechanism of thickness dependent transition from solid to hollow profiles is described by the viscous buckling of metallic liquid. In vitro skin insertion tests demonstrate that both solid and hollow metallic glass microneedles can pierce porcine skin and deliver model drugs.