You can get tetanus from rust but it's not caused by the rust itself and instead the tetanus is caused by the bacteria that can be inside the rust.
Rust does not cause tetanus but the rust can contain bacteria that causes tetanus.
Tetanus is caused by bacteria found in rust, soil etc and not the rust or soil or metal itself.
However rust can contain the bacteria that causes tetanus.
Tetanus is an infection caused by bacteria called Clostridium tetani.
When the bacteria invade the body, they produce a poison (toxin) that causes painful muscle contractions.
Another name for tetanus is “lockjaw”. It often causes a person's neck and jaw muscles to lock, making it hard to open the mouth or swallow.
So if you get cut by rusty metal or step on a rusty nail the rusty nail or metal can contain the tetanus bacteria which is actually what gives you tetanus.
You can even get tetanus from stepping on a clean nail or getting cut with a clean piece of metal.
However you're more likely to get tetanus when stepping on a rusty nail or cutting yourself with a rusty piece of metal.
To prevent tetanus you should get a tetanus shot every 10 years and if you haven't had a tetanus shot within 10 years and you got cut especially with rusty metal or a rusty nail you need to get a tetanus shot.
Tetanus can be deadly if you're not vaccinated for it and you get it and leave it untreated.