They don't
A steel toe shoe is one kind of safety toe shoe.
You cannot get inserts for steel toe shoes. Look for steel toe safety guards. They attach outside your shoe, and are removable. That is your only option beside buying a real safety-toe shoe.
you wear it
Composit toe shoes or boots will feel lighter than their steel toe counterparts.
Composite toe shoes are made up of composite materials, such as plastic and carbon fiber. A steel toe shoe is made up of only steel.
Munro is an American shoe company who focuses on offering a variety of sizes and widths. Currently, Munro does not offer a steel-toe shoe.
Try steel toe safety guards. They attach externally to your shoe, and are removable. That is your only option. Just buy steel toe boots.
A steel toe shoe or boot has a piece of steel inside the tip (about 2 1/2 inches) to protect the toes from being crushed if a heavy object falls on the foot.
Steel toe capped shoes don't always have steel at the cap, but it's always durable metal. This is essential as the shoes need to be hard wearing for work.
A steel-toe boot is a durable boot or shoe that has an protective substance in the toe, usually combined with a sole plate, which protects the foot from falling objects and punctures from below.
A composite toes shoe or boot is one in which a shield is provided in the front to protect the toes from crushing is a heavy weight falls on them. That shield is incorporated into the shoe or boot toe and is made of a "composite" material like Kevlar, carbon fiber, or plastic.