If you say monster, people think of something big, terrifying, fearless. Are you sure you're the best? Then frighten your competitors with your .monster domain name alone, show your fearlessness and distinguish yourself with your .monster name.
Are you passionate about monster trucks? Do you know everything about the fantasy world of the dragons? Or are you one of Lady Gaga's little monsters? Then a domain name under the .monster extension is perfect for you.
Or use .monster to surprise your website visitors. People expect something big, if you do the opposite and write a blog about your kitten or puppy under your .monster domain, everyone will definitely remember this.