The Rambam understands Physics and Metaphysics as the way to fulfill the mitzvas of Love and Fear of God.

Besides the Rambam my own parents saw something important about Physics.
[Though the Rambam's definition of this was a little different than the modern day one. The Rambam openly wrote he was referring to the Physics of the ancient Greeks which means basically Aristotelian Physics. Still the approach and subject matter is that which the Rambam was referring to. The Rambam did also add Metaphysics-which he did also say meant that of the Ancient Greeks. 
But in that case he would have been referring to the subject as it was developed later by Plotinus.

But in these cases, he was not just referring to the writings, but to the subject itself. Similarly in his approach to the Oral Law he divides it into two sections. One is the actual learning of the material which he meant in the sense of learning the Mishne Torah (of the Rambam himself) itself. The other is the  reasoning it out, which is the kind of process we see Reb Chaim Soloveitchik and Rav Shach engaging in. [This process had its beginnings with Rav Joseph Karo, but really came to its summit in the book of Ideas in the Rambam of Rav Soloveitchik and the Avi Ezri. ]

The Rambam understands Physics and Metaphysics as the way to fulfill the mitzvas of Love and Fear of God. This is hinted in the Mishne Torah, but stated openly in the Guide.
[The way that this makes sense to me is by means of Reb Nachman's ideas about the hidden Torah in the work of Creation. And the Hidden Statement of Creation. At least, that is how it makes sense to me.  And it seems to me the Rambam must have been looking at this in a similar fashion, but so far without a copy of the Guide I can't remember a specific place where he might have said this.]

In any case, with the Rambam we get a very elegant way of serving God, that make a lot of sense. It is a balanced approach: The Oral and Written Law of Moses, Physics, Metaphysics. To me this approach has a lot of charm and beauty to it. Besides the fact that it is כיבוד אב ואם honor of my father and mother which is one of the 613, and not a minor one either. 

[You can add this this basic structure to some degree but what ever you add has the danger of being bitul Torah. Bitul Torah the sin of not learning Torah when one has the time to do so.]

(note 1) In the original Musar movement there was the idea of spending as much time as possible learning Ethics {Medieval Musar}, but as you can see that idea was not really accepted in its entirety by the Musar Litvak yeshivas because of the law of limited returns. While important it is, adding to it beyond a half hour daily does not seem to add much.

(note 2) On the side of those that think Physics and Metaphysics are forbidden and also all secular subjects  would have to say that (1) those that supposedly only learn Torah are jerks. I saw enough of this in Israel. Torah without Derech Eretz is not Torah. סופה בטילה. But I have to agree a lot of secular subjects are in fact bitul Torah.

(note 3) Just for the record when I say Physics I am mainly referring to Quantum Field Theory and the later String Theory.  Metaphysics however I think best to confine to Aristotle, Plato, and Plotinus, though I see Hegel and Kant as being pretty important also.

(note 4) The Rambam is not referring to mysticism. Though at the time I was learning Musar and the Arizal, I thought he was. Now this is not to say there is no place for a mystic interpretation of the Guide. We know Rav Avraham Abulafia wrote a mystic commentary on the Guide. Still the Rambam in teh Guide itself says exactly what he meant by Physics and Metaphysics.