Car enthusiasts, especially those with a show-worthy project, often put a lot of thought into the vehicle's color. Whether a car is finished in factory paint or a custom hue, it's often a difficult, but fun, decision to make. Opting to go the bare metal route takes away that potential, but there are other options to add interest to a car's panels. For example, using an angle grinder to polish the car can provide a unique, textured finish; and flash rusting has been used to create areas of contrast or even stencil-like designs.
In some climates, a bare metal car will begin to rust almost immediately -- as soon as the metal comes into contact with any kind of moisture, even just the stickiness in the air on a humid day. To maintain the proper bare metal look, it's necessary to prevent or minimize this effect. Some bare metal cars do have a clear coat, although that approach lacks a little in the authenticity department, and moisture can sometimes still get beneath the surface, allowing rust to become visible beneath the supposedly impenetrable finish. If this option is appealing, there are clear coat products designed specifically to cover bare metal, such as Eastwood's Diamond Clear Gloss.
Waxing works, too, but it's a semi-permanent solution. "Semi" because you'll need to redo it regularly for maintenance, and "permanent" because once you make this choice, you can never go back. Even though the wax coat needs to be maintained, that first application of wax-to-bare-metal adheres and absorbs in a way that can't be removed. If the owner of a bare metal hot rod waxes just once, that one coat is almost guaranteed to cause problems when it's time to go a different route, such as painting. The metal surface will never again be a clean slate.
Lubricants are also a possibility. WD-40 is perhaps one of the best known lubricant products on the market, and it's sometimes recommended for a bare metal car finish -- but it can cause the same problems as wax. Gibbs Brand, however, produces a penetrating oil that is known to be one of the most popular products for bare metal hot rods, and it applies easily with a paper towel. One of the reasons Gibbs Brand is so popular is because it immediately penetrates the smallest pores of the metal surface to prevent oxidation, and it even claims to remove rust. It protects bare metal surfaces like a lubricant, but it can also be painted over, so using Gibbs Brand isn't a point-of-no-return scenario. It's also reported to prevent fingerprints and other such surface stains, which any owner of a stainless steel refrigerator can easily appreciate. Some Gibbs Brand loyalists suggest applying the product immediately to any area of the car that's been freshly stripped of paint; in other words, don't wait until the whole car is bare to start protecting it.
Like any major project, it's important to make wise decisions during the entire process of building a bare metal hot rod, and there are many more in-depth resources available that you can consult along the way. Getting involved in the culture is definitely a good way to learn more about your new project -- and it'll make the end result more enjoyable, too.