This is intended as a sexual comment, where the woman knows her beloved's desire is for sex. She understands he doesn't want just her body but a relationship with her. The human sex drive is one of the strongest we have.
It's rather odd but God has chosen a man's desire for a woman as the best imagery of God's longing to be in relationship with his people. When God uses imagery in this way it isn't sexual but rather God is using the power of sexual desire to describe the strength of his desire to be close to his people.
Other strong human needs are for food, water and shelter. God chooses to employs these images too: Jesus declared, 'I am the bread of life. Whoever comes to me will never go hungry, and whoever believes in me will never be thirsty' (John 6:35). 'He who sits on the throne will shelter them with his presence' (Revelation 7:15).
God wants his people to know the strength of his yearning to be in relationship with them and to be all that they need. He longs to satisfy us with good things. 'The Lord bestows favor and honor; no good thing does he withhold from those whose walk is blameless' (Psalm 84:11).
Likewise he wants us to have the same yearning for him, 'Blessed are those who hunger and thirst for righteousness, for they will be filled' (Matthew 5:6). Yet often our desire for God is relegated to being less important than our longings for wealth, status and significance. God is not able to satisfy us when we are busy trying to satisfy ourselves with the things of this world.
Let's seek God with wholehearted devotion.