It depends on how we define 'matter'...
Matter is something that occupies space and can be perceived by one or more senses; a physical body, a physical substance, or the universe as a whole.
If being Omega means you can effect matter, I don't see why Storm can't be one. 'Matter' itself is way too debatable, I think.
"We live in an age of darkness. But in every age, there are those who fight against it."
X-tremely proud member of the Storm Squad!