Rashi: The Navi says, I will sing li'Ydidi - in place of my beloved and doing His Shelichus. This is like "Hashem Yilachem Lachem" (Shemos 14:14) - for you.

Radak: "Shirah" refers to a parable about the people of his generation. Yisrael are a vineyard, and Hashem is the owner. It is praise of the lover, and his love with the beloved. Similarly, "Shir ha'Shirim li'Shlomo", because it tells of the love of the lover and his beloved, is a parable for Kel and Keneses Yisrael. The Navi calls Hashem "Yedidi" and "Dodi", like "Ki Vi Chashak" (Tehilim 91:14).

Malbim: [The Navi] rebukes Yisrael via a parable and riddle. Yedido is Hashem.

Rashi: It is what he sang for His vineyard, due to the matters of His vineyard. This is like "va'Yish'alu Anshei ha'Makom l'Ishto" (Bereishis 26:7).

Rashi (7): Adam ha'Rishon was the vineyard of li'Ydidi (Hashem).

Malbim: Hashem's relation to Yisrael is depicted as if Hashem had a vineyard that He planted on a tall steep mountain in a fat place. The location obligates that it will succeed [to produce] strong wine.

Rashi #1: In corners, that make fat Peros like good oil.

Rashi #2: In corners proper for oil, i.e. for olives to make oil. "Ben" is like "Ben Maves" (Shmuel II, 12:5) - proper for death.

Rashi (7): It is in Gan Eden.

Radak citing Targum Yonasan: On a tall mountain and a fat land. Eretz Yisrael is called Keren, because it is higher than all lands. It is called Ben Shemen, like it says "Eretz Zavas Chalav u'Devash" (Shemos 3:8).