Put slices of swordfish in a shallow pan. Brush with melted butter. Broil under medium heat for 5 to 7 minutes on each side, basting with drippings in pan. Be sure not to let fish become too dry. Spread lightly with mayonnaise. Season with salt and pepper and sprinkle top with bread crumbs. Baste again with drippings. Broil for a few minutes more or until crumbs are crisp and brown.