Merlot produces nicely colored wines, soft in fruit but capable of great richness.  It is invaluable in Bordeaux, bringing fruity lusciousness and a velvet quality to wines that might otherwise be rather hard and austere.  It is the chief grape in Chateau Petrus, which is the top name in Pomerol. 

Info : The Sotheby's Wine Encyclopedia 4th Ed by Tom Stevenson