While steel can chip, dent or break if it's struck in just the right way, the idea that one sword can fully cleave another one is a fantasy. In other words, it is not plausible that, in the case of two people having a sword fight, one fighter could use his or her sword to make a clean cut through the opponent's sword in order to effectively disarm the opponent.
This idea, which is seen in movies such as "The Count of Monte Cristo," was tested by the Discovery Channel show "Mythbusters." This show's experiments showed that it is not easily possible for one sword to chop another in half.
Another movie myth is that a silk scarf, dropped onto a very good, stationary samurai sword, will be sliced in half. This is unlikely, as the sword is designed to cut objects that they are pulled across.