A query letter is a business letter. Writing may be art but publishing is a business. As a writer you are the creator of a potentially sellable product. Being too weird or unprofessional in your query letter can lessen the chance that you will get your work noticed, published, on bookstore shelves, and into the hands of readers. It’s ok to have personality, be interesting and inventive and perhaps a bit funny. And it’s ok for your work to be weird. Just keep the weird out of your query letter. And remember to check for typos, as that’s part of being professional.
The whole point of a query letter is to get someone to read your manuscript. That means you don’t need to describe every little thing that happens in the plot, or name all the characters, or give away the big secret, or say how it all works out in the end. Unless giving away the big secret will be the thing in your letter that gets someone to read your manuscript… It’s way more important to write an enticing query letter than to spell everything out.
A query letter shouldn’t run longer than one typed page (even though it’s usually an email). Figure on double spaced, 12 point font, 1″ margins. Think 3 or 4 shortish paragraphs. An introductory paragraph with a pitch or a logline, a short synopsis (preferably without spoilers), and a bio with only relevant information. Don’t overthink this but do polish it to a high shine.
There are many places where you can get more detailed information about how to write a query, including lots of past posts on this blog. There are books on writing queries, workshops and breakout sessions at writing conferences, and more places online than I have time to link to. Just try a Google search. And good luck!