Shades of Modality [infographic]: A modal verb is a type of auxiliary verb that expresses possibility, necessity or obligation. Because of their commanding tone, modals must be used carefully, and some writers attempt to avoid them entirely.
“Shoot yourself in the foot” means “to do or say something that causes problems for you”. Example: When Michelle got drunk before her final exam, she shot herself in the foot. She failed the test! Learning English can be fun!