There are a number of preposition words that change the meaning of a phrase when used with a particular word. For example, you can use Useful with different prepositions, and you will get a different meaning every time. You can see the examples below:
1. Useful for
Useful for (thing)
Example: The bag is very much useful for carrying goods.
2. Useful to
Useful to (person)
Example: I found that these directives are useful to me for success in exams.