Californian Merlots tend to more fruit-forward, with lots of raspberry and blackberry cut with strong mocha and chocolate notes. The tannin tends to be softer in warm climates.
Merlot is known for producing an inky, purple juice that varies hugely in complexity depending on the process used to make it.
Merlot is the most commonly known grape variety in France, and is one of the six permitted grapes in the Bordeaux blends. French Merlot tends to exude more complexity in its tannin, earth and minerality.
France and Italy are the highest producers of Merlot. The USA is the 3rd largest producer, with California alone harvesting over 45,000 acres in 2012. Paso Robles and the famous Napa Valley are the most notable regions for Merlot in California.
Merlot benefits hugely from some barrel time, and leaving it to sit in oak for up to 24 months can add huge amount of depth and complexity to the wine, and balance out some of the zealous fruit with oak and vanilla.
A nice, bold Merlot will work famously with a bit of roasted duck or some braised beef.