Written as a direct address to someone the speaker once relied on, "Matter" is about the pain of being met with indifference. The speaker says this person let them contemplate suicide and wouldn't have cared if they had gone through with it. The title works two ways: the speaker feels they no longer matter to this person, and the subject itself matters deeply.
The tone is flat and plain, with short lines and no decoration. That bareness makes the poem feel raw, as if the speaker is stating a hard fact they've had to accept. The pain is admitted quietly: "I can't deny that it hurts."
The most striking moment is the ending. The "final blow" is not a physical act but the knowledge that this person wouldn't care. The last lines suggest that this person once helped the speaker, and now their indifference does the damage instead. The mood is heavy, lonely, and sad.
If the poem reflects something close to you, please consider talking to someone you trust or a local support line.