Not only users but bots and spammers love online forms. And nothing is more annoying than scanning a ton of spam mails for actual inquiries from your users. That’s why your form builder of choice should provide at least one way to prevent spam.
Most form builders have a build in spam-trap. The Honeypot. Just like a real honeypot would catch flies, this honeypot will catch the spam submissions. This technique is popular because it prevents spam without interfering with the user experience.
Basically it will add a field to your form which is invisible to the visitor. Automated software will fill out that field and thus unmask itself. Akismet is the most famous honeypot solution, often used to guard the blog comment fields from abuse.

Another way to stop spam is by adding an additional field that can only be answered by a person. A CAPTCHA. You can find these Anti-Spam-Fields in nearly every page builder.
It’s very effective, however it does not only present a formidable barrier to spambots, but depending on it’s type it can also become a barrier to your leads, contacts, and anyone trying to fill out your form.

Take me as an example: I regularly fail at identifying the “pictures that contain traffic lights”, which means I have to redo the captcha over and over again until I get it right. Unless you are offering to give away money to anyone who survives this procedure, form abandonment will become an issue.
But Captchas have been evolving a lot, and nowadays you can use reCAPTCHA v3 by Google which is completely invisible and uses advanced risk analysis and automated software to prevent spammers.
If you are deciding which form builder to use, have a look at exactly what their Spam protection looks like, and if it is part of the free version, or requires a paid plan.