Contact less electrostatic force microscopy (EFM) and dielectric force microscopy (DFM) are demonstrated to be very powerful tools of characterizing the electronic properties of individual single-walled carbon nanotubes (SWCNTs). Taking the advantages of the tools, we confirm that the metallicity of metallic SWCNTs can be largely preserved upon dichlorocarbene functionalization ([2 + 1] cycloaddition) in comparison with the SWCNTs subject to the Prato reaction ([2 + 3] cycloaddition). This work demonstrates the distinct difference between sp(2) rehybridized and sp(3) rehybridized covalent configurations on their influences to electronic properties of metallic SWCNTs and supports the hypothesis that [2 + 1] cycloaddition could recover the sp(2) hybridization on the sidewall of metallic SWCNTs and preserve the intrinsic electronic properties of SWCNTs.