Employers want staff members that are eager to come to work and are passionate about what they do. They know from experience that these employees tend to perform better than more passive workers.
So be sure to demonstrate your enthusiasm. Let your recipient know why you enjoy your field and express specifically why you think working for their company is an excellent opportunity to do what you love.
If you have an interesting story about how you learned of the position, include it. Anything you can do to personalize the message while demonstrating your passion increases the chances that they’ll peruse your resume.