A cover letter is a personal document, written in the first person, created for one specific job application. Use it to position yourself specifically against the job posting's key requirements and to sell yourself directly into the offered role.

The cover letter must be brief, always less than one full page. It has a contact section, two or three paragraphs of precisely targeted pitch, and a close. You must keep it concise, or the application screener will TL;DR it.

While the tailored-to-the-role nature of the cover letter precludes a generic example, you could follow my template below to get started.

Section one – Name and basic contact information

Home town, Province/State/Region
Phone number
email address
Hyperlink to LinkedIn profile

Notes: No precise location or street address is needed. The prospective employer will not send you surface mail or come to your house. Unless they send a drone.... Phone number and email address are a given, the employer may use either mechanism to contact you. A current and complete LinkedIn profile is a must-have for any professional, it augments and expands upon your resume. Any other on-line presence (social media, GitHub, etc.) should be mentioned on your resume and/or LinkedIn, not here.

Section two – Date and position, salutation

{Date of application}
Re: {Position name} at {employer} {, Reference ID (if provided in the job posting)}
Dear {Name of recruiter or hiring manager, if known}

Notes: Career counselors recommend that you work to find out who will be reviewing your resume and out their name on the cover letter. As a former hiring manager, I found this weird and stalker-ish, so I don't do it. YMMV.

Section three – The pitch

I am a {thing you want to be hired to do} with proven experience {doing one of the key requirements of the job posting}. I have consistently {done another primary thing from the posting} while also {doing yet another thing that they want}. I have {done other relevant things specifically mentioned in the job description}.

I had proven success in my previous role at {old company or school} as a {what you were called there}. {List a set of relevant accomplishments that back up your claim to success.}

Notes: The first paragraph has your best matches to the role. If you don't have anything, you'll need to go with an explanation of why you're so keen to do this thing that you have no experience doing, and hope for the best. The second paragraph has more latitude to highlight other accomplishments or soft skills that might intrigue the screener. But keep it tight! Laser focus is key, resume screening is a grind, and a wall of text is going to be skipped, no matter how clever or well-worded it is.

Option: For a role with detailed technical requirements, a two-column table matching the requirements to your skills can be used. This works best if the job description uses a set of specific must-haves that can be described in a few words each. I have chosen to interview, and ultimately hired, software developers who used this technique to show that they could pick out the key parts of the role and respond to them.

Section four – The close

I feel that my extensive experience is a great match for the posted role. I would love to meet to discuss this opportunity further, to learn more about your needs, and to explore how I can become a part of your exciting organization.

{Your Name Here}

Notes: This is the boilerplate bit. "I am a great fit, let's talk." Again, if you don't have the experience, go with "enthusiasm and desire," and hope that they decide to take a chance on you. Repeating your name may seem redundant but it suggests your signature as it would have appeared on a physical letter in the last millennium.

Good luck, and may the Force be with you, always.