Muslims believe that the Quran is the Last Testament of Allah and it is the confirmation and completion of the Guidance of Allah to humanity contained in the previous Books.

 Muslim scholars have noted clear and undeniable prophecies found in the Bible (both Jewish and Christian) about the coming of the final prophet. When these verses are quoted, the usual response of many Jews and Christians is a staunch denial of any such possibility.

 And among those who have cared to examine the Muslim evidences were unbiased persons who were eventually convinced of the truth of Islam and have subsequently become Muslims.

As you have said, one of these prophetic verses is from the Song of Solomon. Before we explain the context and meaning of the quoted verse, we need to understand the subject of the Song of Solomon, and why it is considered a holy book inspired by God Almighty.

 Here, I quote the learned view of a Christian Bible scholar on the Song of Solomon:

 "This book has received more varied interpretations than perhaps any other book in the Bible. Some writers believe it presents the reader with the "greatest hermeneutical challenge in the Old Testament. One excellent exegete called it "the most obscure book in the Old Testament" (Franz Delitzsch: Biblical Commentary on the Song of Songs and Ecclesiastes, quoted by Dr Thomas L. Constable in his Notes on Song of Solomon)

There is no doubt that the Song of Solomon has a unique place among the books of the Bible. Because, it is a love poem. Naturally, no one expects a love poem to be part of the Book revealed by God Almighty. Let us consider this question from the Christian point of view:

The Christian scholars quote the following verse from Paul's Second Epistle to Timothy as giving clear criteria for judging inspired scripture:

"All scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness." (2 Timothy 3:16, KJV)

There need not be any controversy about the idea expressed above: Whatever is believed to have been revealed or inspired by God must serve one of the four purposes: Either (1) it must teach us doctrine; or (2) it must reprove us for our error; or (3) it offers us correction; or (4) it guides us into righteousness.

On examination, we can find the Song of Solomon failing to pass any of the above criteria. Because, from a religious point of view: (1) it does not teach any doctrine; nor does it mention even God; (2) it does not reprove us for any error on our part; (3) it does not offer us any sort of correction; and (4) it does not guide us into righteousness; rather it gives sensuous descriptions of physical intimacy in a frank language in a Book of God.

Indeed the difficulty of providing it a meaningful interpretation has caused some Christian readers to doubt its status as a part of scripture.

The Song is apparently sung by Solomon in admiration of one woman, and it depicts faithful love to that woman; but Solomon had 700 wives and 300 concubines (1 Kings 11:3). This fact alone should be enough to cast doubts on the claim that Solomon wrote the Song in admiration of his sweetheart — i.e. a single person — glorifying fidelity and sincerity in love.

The only possible apology for the inclusion of the Song in the Bible can come from the view that it is an allegory. A majority of interpreters favor this view.

To them, what the writer said was only a symbolic husk for a deeper spiritual meaning that the reader must discover. (Greg W. Parsons:  "Guidelines for Understanding and Utilizing the Song of Songs," Bibliotheca Sacra 156:624 (October-December 1999):399-422; quoted by Dr Thomas L. Constable in his Notes on Song of Solomon)

Viewed from this angle, it would be wrong to take the Song of Solomon literally. Chiefly, because a love story for the sake of a love story does not have any place in scripture.

This means that the Christians have to take one of the two reasonable positions: Either they should consider the Song of Songs as non-canonical and reject it as possessing any scriptural value, or they should be prepared to accept it as an allegory, where language is used symbolically. And then the love story suddenly takes on new meanings which it did not possess before.

And remember, a symbol is "something used for or regarded as representing something else" (Dictionary.com).

Now, let us take a closer look at the verse quoted:

"His mouth is most sweet: yea, he is altogether lovely. This is my beloved, and this is my friend, O daughters of Jerusalem." (Song of Solomon 5:16)

The original Hebrew Bible has "Muhammadim" in the place of "altogether lovely", but the translators rendered it "altogether lovely". It should have been "the Praised One" — that is the correct meaning of "Muhammadim". At the same time, "Muhammadim" happens to contain the name of the final prophet in Arabic too. This is what Muslims are quick to point out.

They (with very few exceptions) do not study the context of the expression as found in the present Bible. The Christian contention is that the context does not warrant any one to claim that there is a clear reference here to the final prophet.

Now, after considering the whole of the Song of Solomon and the context of the verse, we can say that if we take the Song as an allegory, and the epithet, "Muhammadim" as a description of "the beloved", it is possible that the beloved is someone for whom a nation — or the world — was waiting (for instance). And as has been argued above, there is a strong case for that.

I want to underscore this point again. The Christian claim about the Song of Solomon, that it just tells a good love story, seems to contradict their defense of the Song as divinely inspired as the rest of the Bible.