While Merlot is the most widely grown grape variety in France, seems to have originated in Bordeaux, and accounts for over half of the region’s vineyards it was not recognised as a separate variety until 1784. The name derives from the French word for blackbird, either for the dark-blue fruit or because blackbirds are fond of the ripe grapes.

French plantings account for nearly two-thirds of the world's Merlot, but it is grown across the globe, often in cooler sections of regions that produce Cabernet Sauvignon. Merlot ripens a week to ten days earlier than Cabernet.

Research at the University of California, Davis suggests Merlot may be a mutation of Cabernet Franc, and it bears a strong resemblance to Cabernet Sauvignon (hardly surprising, since Cabernet Sauvignon is a cross of Cabernet Franc and Sauvignon Blanc) and Carmenère, a variety that disappeared in France in the wake of the phylloxera epidemic. Chilean producers had been labelling wines made from that variety as Merlot, an error that was identified in the 1990s after vineyards thought to be planted with Sauvignon Blanc were found to be growing Sauvignonasse. In the wake of that discovery, genetic studies revealed much Chilean Merlot was Carmenère, While the vines, leaves and grapes look similar, Carmenère is strongly flavoured with green pepper notes while Merlot displays softer fruit with chocolate notes.

Although it may be related to Cabernet Sauvignon, Merlot grapes aren’t as intensely coloured, have a thinner skin, a higher sugar content, lower malic acid and fewer tannins. The wines have a softer texture and are more approachable than young Cabernet. Like Cabernet, cool climate Merlot can exhibit grassy and bell-pepper notes and it develops blackcurrant, blackberry, blueberry, chocolate and spice-like characters when fully ripe.

Merlot is often blended with Cabernet Sauvignon since the softer texture, plummy fruit and mellow tannins counterbalance the sterner tannins of the Cabernet while the Cabernet adds length of palate. This combination may be varied with Cabernet Franc or Malbec as in Bordeaux, with variations to allow for regional and local characteristics and vintage conditions. Cabernet Sauvignon dominates the blends of the Médoc and Graves, where the soils are warm and gravelly, while Merlot prevails in the iron-clay and limestone soils in Pomerol and St.-Emilion. In limestone, the variety tends to develop more perfumed notes and coming off sandy soils the wines are softer than Merlot grown in clay dominant soils.

Vigorous vines produce loosely knit conical bunches of medium sized round thin-skinned blue-violet berries high in colour and sugar, but not very tannic. The grapes are thin susceptible to fungus and mould, and since Merlot shoots early it is more likely to be affected by frost. In areas that are too warm, Merlot can ripen too early, needs to be picked at optimum ripeness and if overcropped, it produces pale, weedy, vegetal wines.

Varietal Merlot and Merlot-based wines are usually soft, fleshy, velvety medium bodied wines with a supple mid-palate, and hints of (among other things) cassis, cherries, blackberry, plum, mint, currant, spice, earth, tobacco, leather and chocolate. Velvety tannins generally make Merlot a good early drinking style, even when the wine is designed improve with age. As a medium bodied wine, Merlot suits the more subtle French rather than American oak, and when the wine is given significant oak treatment, the result is an array of caramel, chocolate, coconut, coffee bean, mocha, molasses, smoke, vanilla and walnut notes.

Merlot is grown in most Australian regions, but Australia's best examples come from cooler areas including the Adelaide Hills, Eden Valley, Orange and the Limestone Coast (including Coonawarra).

Merlot is a good match for grilled meat, pasta, roasts or Mediterranean vegetables, while softer, fruitier styles from cooler climates can go with salmon and mushroom-based dishes. Merlot tends not to go well with strong cheeses that can overwhelm the fruit flavours of the wine, so for cheese, pate or game, a Cabernet Merlot blend, with acidity and tannin from the Cabernet would work better than a varietal Merlot.