wallflower

(noun) a person who is shy at social events, especially someone who doesn’t like dancing with other people

Example Sentences:

Whenever I go to a party, I am always a wallflower because I hate meeting new people.

William was a wallflower at the party. When everyone was dancing, he was just leaning against the wall.

Media:

Similar idioms:

1. take charge of
2. creeper
3. drive someone up a wall
4. the writing is on the wall
5. be banging one’s head against the wall
6. beat one’s head against the wall