The speaker stands on a ledge and points out the camp fires of "my brothers" burning in the dark. Right away we sense pride and belonging. The speaker is addressing an "you", perhaps an outsider or visitor, and showing off a people who are not hiding. Lighting fires where anyone can see them is a kind of boldness.
The Highlanders are described in quick, hard details: they are "goat sure in the dark," at home in rough country where others would stumble, and each carries "a dirk in every pleat," a dagger tucked into the folds of the kilt. That detail adds a note of warning. The ending shifts the mood. Their pipes carry across ravines, "mentioning their dead," so the music is a kind of remembering. The poem feels proud, watchful and a little menacing, but grief runs underneath. These are fierce people who keep their lost close, and the speaker shares in both.