As a hiring manager, I always like to see at least a few short sentences. At a minimum you should share a point or two of why you are a good fit for the role. I

As a hiring manager, I always like to see at least a few short sentences. At a minimum you should share a point or two of why you are a good fit for the role. It doesn't need to be overly formal and could just be along the lines of: "Hello, I noticed that you have a position open using [tech]. I am very familiar with [tech] and have been using it for [x] years. I saw on your website that your company is building a solution to [business model], [show your interest in business model]." A longer letter is OK, but I don't really value a generic long-form letter any more than a short note showing you are paying attention and have real interest in a role at the company.