The speaker starts by trying on a comparison: "say I am a snowflake." Snowflakes are delicate, cold, and each one is different, and the speaker admits to feeling a little like that, fragile and a bit awkward about being unusual. The phrase "for once" suggests they don't usually describe themselves this way, so it feels like a small, slightly shy confession.
Then the poem turns. Whether the snowflake comparison is true or not, the speaker says, "I melt every time we touch." The real point isn't how they see themselves but what another person does to them. Cold and guarded on the surface, they lose all that the moment they're touched. The mood is tender and vulnerable, with a hint of humor in the offhand tone. The short lines make it feel quiet and hesitant, as if the speaker is almost whispering the last line.