Most meat needs a certain amount of fat in it to prevent it from drying out during cooking. Barbeque connoisseurs will never look for lean steaks; they look for steaks with good marbling.
Barding is a fancy word for a technique you probably already practise. You tie a piece of fat, such as suet or American-style bacon (streaky bacon), around a piece of lean meat or poultry so that the added fat compensates for the absence of fat to keep the meat or poultry moist. A few minutes before the meat is done, you remove the fat to allow the meat to brown.
If you use American-style (streaky) bacon, you can salt the meat a bit less as some of the salt from the bacon will go into the meat.
Cooking Tips
You may want to use unsmoked bacon (as opposed to smoked bacon) with beef.