There is only one thing that makes a lead magnet truly magnetic, and that is relevance. The email’s content should solve a specific problem of the recipient, and this can start with the content of the page where the email address was entered.
A lead magnet can be defined in many ways, but essentially, it is an offer made at zero cost to the consumer, in exchange for an email address and additional details useful to the marketer. Because of its wide scope, a lead magnet is often called other names, such as a sign-up incentive or a freemium.