Lithium (Li) metal anode attracted tremendous attention nowadays as a promising electrode for the next generation of rechargeable batteries. However, the uncontrollable volume change and severe dendrite formation raise safety concerns that hindered the implementation of Li metal anodes in rechargeable batteries for decades. Herein, we introduce a novel stable and flexible Li metal felt anode using thermal Li infiltration method. The structure revealed unprecedented cycling stability for 500 cycles under ultra-high current density of 40 mA cm-2. Also, it sustained its mechanical flexibility even after Li infiltration. Finite element multiphysics models were demonstrated, which illustrate in detail the fundamentals behind the outstanding stability of the Li felt. Moreover, the electrochemical full cell test comprising Li felt as anode and LiFePO4 as cathode, exhibited 7-fold higher discharging capacity of 70 mA h g-1 at 10 oC, corresponding to only 10 mA h g-1 for Li foil. On the other hand, the method reported in this study allows the entire process to be easily scaled up for industrial scale with roll-to-roll manufacturing. We believe that this novel structure will pave a new avenue towards promoting the performance of Li metal rechargeable batteries and hence making it finally practical for commercial applications.