The Phonogram co-creator was revealed to be joining Matt Fraction's Marvel Comics series from issue #8 during Chicago's C2E2 convention on the weekend.
"Matt writes the most inspirational scripts for an artist," McKelvie told iFanboy.
"He's also really great to throw ideas around with, lots of back and forth emails as we plan story and design and so on."
"You really have to think about what makes each character different, so they don't end up looking like the same doll dressed in a different outfit," he contined regarding his work on Marvel team books.
"Personality, body language, and so on. It's especially important with a team like X-Men where they all wore the same uniform, but it applies to the The Defenders too."
McKelvie collaborated with Dennis Hopeless on Marvel's X-Men: Season One original graphic novel.
He is due reunite with Kieron Gillen on a new Phonogram miniseries from Image Comics.
The Defenders #8 will be released in July.