Whom is a personal pronoun that is one of the most formal pronouns in the English language. It is used as a subject pronoun, object pronoun, and with prepositions.
when used as a subject pronoun, it will typically follow a verb but can also replace an object. In this capacity, it refers to the people or things for which the action of the verb has been done. For example, 'Whom did you give the money to?' When used as an object pronoun, it typically follows a preposition and will refer to a person to whom the action of the verb is being done. For example 'With whom are you going dancing?.' When used with prepositions, it typically follows the preposition and can refer to either a person or thing. For example 'Whom are you talking to?'
1. Whom did you invite to the party?
2. To whom did he write the letter?
3. With whom did you go to the beach?
Whom should only be used when referring to either people or things and should not be confused with other pronouns like who. Additionally, it is important to remember that a sentence with whom typically requires a verb. Without a verb, whom may be used incorrectly. Lastly, when using whom with prepositions, it should always be followed by a verb.