If the top of your tablesaw or bandsaw is starting to rust, you can remove it
by abrading it away. Sanding the metal top removes the
rust but also leaves scratches. You will need to sand with finer and finer
sandpaper to remove the scratches from the previous grit.
I would start with a somewhat fine grit so you don't get overly aggressive and can see how quickly things move along. 320 or 400 grit wet-dry paper with some mineral spirits as a lubricating agent would be a good start. Very mild rust may come off with a nylon Scotchbrite Pad. If the rust removal is slow going, step down a grit. Once you have all the rust off, you can stop there or step up to the next grit to remove the previous grit's scratches. There are also rust removal products available such as Rust Free that work to remove surface rust and light to moderate scale from iron surfaces. Rust Free works quickly and won't harm your tools, so severe cases can even be left to soak overnight.
Deep rust can cause pitting that you may not be able to remove with simple sanding. However, while perhaps unsightly, small pitting should not impede the function of the tool. With severe pitting, surface grinding at a machine shop would be necessary.
There are many aftermarket coating products you can apply to help fight rust formation. You can use simple paste floor wax that you spread out and then buff smooth when dry (like you would when waxing a car). Use floor wax only, however, never automotive wax or polish, as they contain silicone which can interfere with wood finishing. Other products such as CRC Table Guard and Top Cote spray on and form an invisible film to keep moisture at bay. Another product, Boeshield T-9, is for long-term rust prevention when storing your tools. It has a waxy emulsion that creates a barrier that lasts for months. The coating should be cleaned off before using the machine. To remove the film when it's time to put your tools back into service, just spray on a fresh coat of Boeshield and then wipe off thoroughly.
You can also help prevent rust by using a vapor corrosion inhibitor (VCI) such as a Bull Frog Rust Blocker Shield. VCIs are water-based non-polluting molecular coatings that protect metals in enclosed spaces for a year or more at a time. The VCIs bond electrochemically to metal surfaces, yet leave no build-up of oil or wax to contaminate your hands or work.
It's always best to try to remove any surface rust the moment you notice its presence. Sandflex Rust Erasers work extraordinarily well to remove light rusting or spots of rust beginning to form on surfaces. The longer rust lingers on a metal surface, the deeper it penetrates and the more elbow grease you'll need to use to get rid of it.
Remember, rust never sleeps!