How should she be like a signet on his heart?
Rashi: Due to that love, sign me on Your heart, that You will not forget me.
Seforno: Remember me on Your heart.
Malbim (Melitzah): He should cling her to Him in desire and action. Since she had a constant difficult war against the Yetzer ha'Ra and defeated it, it is proper that she be like a signet on His desire and arm, to give to her reward in desire and in deed.
Malbim (Mashal): He should guard her from the king's anger.
How should she be like a signet on his arm?
Seforno: Bare Your Kadosh arm in the eyes of the entire land.
Malbim (Melitzah): Refer to 8:6:1:3.
Why does she say "Ki Azah ka'Maves Ahavah"?
Rashi: The love that I loved You is equal to my death - I am killed for You!
Seforno: [Our love for You is fierce,] even though our deeds are not good.
Malbim (Mashal): She risked her life for his love.
How is "Kasheh chi'Sh'ol Kin'ah"?
Rashi: The conflict that the nations envied and fought me due to You. Kin'ah is an anger that arouses the heart to take vengeance.
Seforno: Kin'ah is in our heart.
Malbim (Melitzah): Kin'ah of the Yetzer is harsh like the pit (grave). It wanted to veer her from Avodas Hashem, and put Keru'eha 1 in the depths of the pit.
Malbim (Mashal): The king's Kin'ah is fierce, that she abandoned him.
Keru'eha are her invitees. Perhaps it refers to bodily powers. (PF)
Why does it say "Esh Shalhevesyah"?
Rashi: Flames of a strong fire that come from the flame of Gehinom. The Trup (note) on "Esh" shows that it is Samuch to Shalhevesyah - the fire of Shalhevesyah.
Seforno: Kin'ah is like a burning fire in our bones.
Malbim (Melitzah): The flames of Ahavas Hashem burned in our hearts. They burned the ropes of the pit and the enticements of the Yetzer.
Malbim (Mashal): Her flames of love are greater than the fire of She'ol (Gehinom), for they are flames of Hashem's flame.