In the first stanza there is a metaphor conferring eye lids to curtains saying to lift them. After it they used some imagery by saying let their light outshine. In this stanza there were more positive words than there were negative
In the second stanza they used two metaphors. They said to pour forth that holy strain and there music is pouring out like a fount of music. Its coming from their inner most core.
In the last stanza there isn't much going on. James Russell Lowell put one part of figurative language and it is an hyperbole. He says "Far, far above earth's atmosphere I rise, whene'er thy voice I hear. This means whenever God calls on him he will go.