There are 3 types of steels:

Metal steels can be used on all knives (except ceramic ones).

Diamond steels are usually flat and can often be expensive.

High-end ceramic steels can tend to be more expensive than your knife.

Diamond and ceramic steels actually remove some shavings from the blade. They can actually sharpen as well as hone or align your knife’s edge. They are even capable of removing some microscopic shavings from the blade. This has the advantage of keeping a knife sharp, even if it has not been honed with every use. Many chefs prefer a diamond or ceramic steel for this reason, but those that hone ritually, every time they use their knife, see little or no difference between the two.

The key remains the same: buy a quality steel and use it regularly or as often as possible.