Whisk together soy sauce, vegetable oil, sherry, ginger root, and garlic in a medium bowl. Fill a large resealable bag with the mixture. Place swordfish steaks into the bag and shake to coat. Place bag in the refrigerator, and allow the steaks to marinate, at least 4 hours.
Preheat an outdoor grill for high heat and lightly oil grate.
Grill swordfish steaks until the they flake easily and are opaque in the center, 8 to 10 minutes per side.