The pairing logic, in depth
The steak-and-red-wine pairing is the most reliable in all of food and wine, and it's not tradition - it's chemistry. Tannins are astringent compounds that bind to proteins and fats. On their own (a young Cabernet with nothing to eat) they taste harsh and drying. Put them against a fatty, protein-rich steak and the tannin grabs the fat instead of your saliva: the wine suddenly tastes softer and fruitier, and your palate is wiped clean for the next bite. The beef, in turn, tastes less heavy. Both sides improve.
Match intensity to the cut. A heavily marbled ribeye has the most fat, so it can - and should - take the most tannin and body: a young Napa Cabernet or a structured Bordeaux. A filet mignon is lean and delicate; a wall of tannin there has no fat to bind to and just tastes aggressive, so reach for a plusher Merlot or a softer, older Cabernet. Strip and sirloin sit in between, where Malbec and Tempranillo shine.
Sauce and preparation are the second dial. A peppercorn crust pulls you toward Syrah, whose natural cracked-pepper note becomes a duet rather than a clash. Char from the grill flatters the faintly smoky dark fruit of Shiraz and Zinfandel. A blue-cheese or compound-butter finish raises the fat and salt so high that you need to size up again - a bigger Cabernet or a Brunello - or the wine vanishes underneath it.
Two practical notes. Serve big reds at 62-66°F, not warm - over-warm Cabernet tastes alcoholic and loses its edge. And give a young, tannic bottle 30-60 minutes of air (or a quick decant) before a steak; it softens the tannin so the pairing clicks from the first pour instead of the third.