Resumes show what you did. Cover letters explain why you are doing something new.
If you are switching from marketing to software engineering, your resume might look confusing ("Why does this marketer have a GitHub link?"). The cover letter connects the dots.
The "Throughline" Narrative
Find the common thread between your old career and your new one.
- Marketing to Dev: "I got tired of manually analyzing data, so I wrote Python scripts to automate it. That's when I realized I loved code more than campaigns."
- Sales to PM: "Listening to customer complaints for 5 years taught me exactly what features users actually need."
Address the Gap Head-On
Don't hide it. "While my background is in [Field A], my recent certification in [Field B] combined with my domain knowledge makes me unique..."
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Complete Guide:
The Complete Cover Letter Guide 2026