Rashi: They will put their hearts to understand verses in two ways - the Mashal and the Melitzah. They will understand for what the Melitzah is a Mashal (parable). Also, they will not veer their hearts from the Melitzah; also it must be understood. E.g. "Lehatzilecha me'Ishah Zarah mi'Nochriyah" (2:16), this refers to the follies of Egypt. The Mashal and also the Melitzah, which used an expression of a woman, understand it, and beware of a foreign woman (some texts - Zonah).

Malbim: This explains the form of the Sefer. It has Mashal and Melitzah. Melitzah is the Nimshal. They will understand also Meshalim of the Torah - the inner idea under the external clothing (Mashal). E.g. stories of Etz ha'Da'as, the snake

Rashi: They expound matters in verses - words written full or lacking (Vov's and Yud's that are not pronounced), hints, comparisons and riddles.

Malbim: This is in oral Torah, what Chachamim said to explain Mitzvos of the Torah and ethical teachings, and Agados and hidden matters that they said in the way of a riddle. Only Chachmei Lev will understand them and find answers, via the Meshalim in this Sefer.