The fattiness of the beef is paired down by the red wine, while the acidity of the red wine is paired down by the fattiness of the beef, leaving you with a balanced juicy burger.
There are a few ways to marinate burgers in red wine. You could put formed patties in red wine for several hours, or you can mix red wine reduction sauce right into the patty mix.
For beef burgers, especially those with an ideal lean-to-fat ratio of 90/10, use a bold red like Merlot or Pinot Noir. Their intense flavors pair really well with the meat.
For a red wine marinade, place burger patties in a shallow dish or air-tight freezer bag and add wine. You can infuse the marinade with aromatics like garlic, sage, and thyme.
To make a red wine reduction sauce, boil the wine and some sugar down to about half their original volume. Take the resulting sauce and add some to the burger mix.
When the burgers hit the grill you will immediately notice the rich aromas of the wine and beef, and it will have an excellent sear and caramelization.