Even grammar can be "moody," but grammatical moods express the attitude of what a person is writing or saying. The three grammatical moods commonly used in English are the indicative, imperative, and subjunctive moods.
The indicative (or realis) mood is used to make a statement of fact:
You cannot outlast us and we will defeat you.
Caption 19, Barack Obama's Inauguration Day: Obama's Speech
You will learn the true nature of the society we live in.
Caption 41, George Orwell's Nineteen Eighty-four: BBC TV Movie
The imperative mood is for commands or requests:
Step away from your vehicle and put your hands on your head.
Captions 10-11, Movie Trailers: Men In Black
All emergency service cars please come to Vesey and West Streets!
Caption 4, World Trade Center: Story on the 2006 film
The subjunctive mood is used to express a a wish, desire, or something that has not yet happened.
I'd like to have something interesting to do and I'd like to have nothing to do.
Caption 54, Leonard Nimoy: Talking about Mr. Spock
I would like to explain how we talk about the time in English.
Caption 3: Lydia explains: the clock