Employees can offer matches more than 100%, and can also offer contributions that are not tied to your contributions. This increases participation without forcing employees to contribute, which helps employers pass the "highly compensated employee" test and allow all employees to fully participate.
For example, an employer may contribute 5% of your salary (sometimes called a "Safe Harbor" contribution), plus a 100% match up to 5% of your salary. So if an employee makes $390k, they can contribute 5% (which results in the individual max of 19,500), the employer matches 5%, and provides another 5% for a total of $58,500. The employer contributions would be limited to 37,500 due to the total contribution limit.
Obviously you can change those numbers for different levels of salary and contribution levels.