מתי משתמשים בhave?

אני יודע את כל האלו אבל לפעמים אני פשוט רואה את זה במשפטים I've ever uploaded ואני לא כל כך מבין את ההקשר. אני יודע להכניס את זה במשפט שאני יודע שצריך, אנע פשוט לא יודע מתי.

Tom eats chocolat
chocolat is eaten by Tom

Tom will eat chocolat
chocolat will be eaten by Tom

Tom ate chocolat
chocolat was eaten by Tom

Tom is eating chocolat
chocolat is being eaten by Tom

Ton must eat chocolat
Chocolat must be eaten by Tom

Tom is going to eat chocolat
Chocolat is going to be eaten by Tom

Tom has to eat chocolat
Chocolat has to be eaten by Tom

Tom has a cake
A cake has been eaten

Tom should eat a cake
A cake should have been eaten by Tom

Tom was eating chocolat
A chocolat was being eaten by Tom