if you are a heterosexual, or may at any time in the future have penis-in-vagina type sex, you should learn a little bit more about contraception. that is absolutely not how any IUD works.
Yes, IUDs are hormonal and don't act as a physical barrier themselves. However, with the hormonal mechanisms, they thicken the cervical mucus, which does serve to block sperm from entering. Perhaps it would be best for you to learn a little bit more about contraception.