Song of Songs (also called Song of Solomon, but which shouldn't be confused with the novel that bears the same name written by Toni Morrison) is, in many ways, a 'classic' love poem. The woman who seems to be co-narrating, swooning with love, compares her lover to all the beautiful and good things in life. In portions of the book such as Chapter 2, the subject seems like cliché and characteristic language of love: chirping birds, sunshine, and flowers. However, King Solomon uses figurative and literary devices, especially in Chapter 8, that are much deeper than the hearts and flowers standby of love poetry. In Chapter 8, the narrator urges his lover to "Place [him] like a seal over [her] heart,/like a seal upon your arm," (lines 31-32). This is an allusion to the seals that royalty and aristocracy would own as personalized stamps of ownership or approval. Placing someone as a "seal" on their body is like a figurative modern-day equivalent of tattooing your lover's name on your body; doing so serves as an attempt to claim the person as your own, branding the body as belonging only to the other.
6 Set me as a seal upon thine heart, as a seal upon thine arm: for love is strong as death; jealousy is cruel as the grave: the coals thereof are coals of fire, which hath a most vehement flame. 7 Many waters cannot quench love, neither can the floods drown it: if a man would give all the substance of his house for love, it would utterly be contemned. (NKJ)
6 Place me like a seal over your heart,
like a seal on your arm;
for love is as strong as death,
its jealousy unyielding as the grave. It burns like blazing fire,
like a mighty flame.
7 Many waters cannot quench love;
rivers cannot wash it away.
If one were to give
all the wealth of his house for love,
it would be utterly scorned.(NIV)
A "love and death" theme is clear in lines (or verses, rather) 33-38 of Chapter 8. During the time period in which the book was written, "waters" and "rivers" were metaphors for death. Put succinctly, one would say that the central theme of Chapter 8 is that love is so strong that not even death can hold it down.