Atomic hydrogen interaction onto the 3C-SiC(100) 3x2 surface is investigated by synchrotron radiation based photoemission spectroscopies, atom resolved scanning tunneling microscopy and spectroscopy, and infrared absorption spectroscopy. Contrary to its well-known role in semiconductor surface passivation, atomic hydrogen is found to metallize the 3C-SiC(100) 3x2 surface. This unexpected behavior results from an asymmetric attack of the Si-dimers located below the surface, leading to charge transfer and to metallization. Interestingly, the H-covered 3C-SiC(100) 3x2 surface metallization is not removed by oxygen.