When do you use "whom?"?

Answer 1

You use whom in the objective sense. When the "whom" is not the subject of the sentence. For instance:
"Who did you give your car to?" (who is the subject of the sentence)
"To all of my friends to use, three of whom do not have cars of their own" (whom isn't the subject of that sentence, 'all of my friends' is)

Answer 2

To whom/anyone it may concern. Whom is used to address a variety of people.

Answer 3

Use the word 'whom' in any sentence in which you could also use 'him' or 'her', for example, 'You are going with him/her/whom'. Use 'who' when you could instead use he or she, as in 'He/she/who is here'.

Answer 4

"Whom" is objective (vs nominative). Use it as the object of a preposition as in "You're going with whom?" or as a direct or indirect object as in "You threw whom the ball?"

Answer 5

In some letters if you dont know who to address the letter to.

Answer 6

Use it when you want to socially embarrass yourself.