2) Matter is an incident, an experience, a situation - another noun.
3) Matter is a condition of being significant, to be consequential - a verb.
We can just be matter (#1), or we participate in a matter (#2), or we can actually matter (#3).
#1 requires little of us, #2 requires a bit more, #3 requires a LOT.
We can matter little or we can matter a lot. It's our choice.
And, it matters.
"In fact, we're capable of creating work that matters only if we're willing to be uncomfortable while we do it." - Seth Godin (2014)