Albert Barnes Commentary 1 Kings 4:32

"And he spake three thousand proverbs; and his songs were a thousand and five." — 1 Kings 4:32 (ASV)

Proverbs - In the collection that forms the "Book of Proverbs," only a small portion has been preserved—certainly fewer than one thousand of the three thousand. Ecclesiastes, if it is Solomon's, would add between one hundred and two hundred more proverbs. But the vast majority of Solomon's proverbs have perished.

Songs - Of these, the Song of Solomon is probably one (as a marginal reference suggests). Psalms 72 and Psalm 127:1-5 may also be among them. Probably, the vast majority of Solomon's songs were secular in character and consequently were not introduced into the canon of Scripture.