Metathesis is the name given to a particular type of chemical reaction – we may refer to the same reaction a displacement reaction. It is not a redox reaction.
An example of this type of reaction is given below:
Image kindly reproduced according to the licence at: http://en.wikipedia.org/wiki/File:Metathesis_reaction_Chemical_equation.png
A metathesis reaction won three chemists (Chauvin, Grubbs and Schrock) the noble prize in 2005 (click here to read more) for essentially producing a catalyst that reduced the number of steps needed for chemical synthesis.