Contact resistance between a multiwalled carbon nanotube (MWNT) and a metal electrode is governed by the contact structure. The relationship between the contact structure and electrical resistance was examined by in situ transmission electron microscopy using a nickel electrode and MWNTs with two kinds of tip structure; close-capped and open-ended. When the current density through the contact region reached a threshold value about 7.6 Â 10 8 A/cm 2 , the MWNT tip was embedded below the nickel surface by local melting of the metal, and the contact resistance was reduced. In the case of the open-ended MWNT, significant reduction of the contact resistance was observed, because inner shells of the MWNT with open cap can connect directly with the electrode.