As in Song of Solomon 2:8–17, the man in this verse seems to have come from quite a distance at night to seek her out, since his head is wet with dew. In the previous chapter, the woman’s abundant moisture symbolized her readiness to receive the man; here his wetness symbolizes the frustrating reality of being shut out of his own house.1 It is also quite possible that describing his head as wet with dew gives a surface motivation for his wanting to come into her warmth and alerts us to the state of his arousal.2 Again, this is not describing literal events, but is a metaphorical description of her experience of her husband approaching her for sexual intimacy.
2 I slept, but my heart was awake. A sound! My beloved is knocking. “Open to me, my sister, my love, my dove, my perfect one, for my head is wet with dew, my locks with the drops of the night.”