Most of the lines start with "I believe..." or "I believe you...." This repetition is a device called anaphora. Its function here is to indicate the completeness of the narrator's belief.
I also noticed two merisms, a device where two opposites are named in order to indicate a broad range. "I believe you on a sunny day" (the first line of the first verse) is paired with "I believe you on a rainy night" (the first line of the second verse), and in an-other section, "I believe you warm" is paired with "I believe you cold." Regardless of what the conditions may be, the narrator still "believe[s] you."
