Metaphysics is the study of Allah (may His Majesty be exalted) سبحانه و تعالى in relation to His ongoing Self-manifestation or - in other words - understanding the relationship between Allah’s unity and the world’s multiplicity - all through the vehicle of the Islamic revelation.
It is not a branch of philosophy or a mental exercise, but a super-rational knowledge, intuitive and immediate.
Tawhid or the assertion of the unique Unity of existence (and of non-existence) demands that all entities, forms and relationships are governed by a single, supreme Reality, the One, Supreme Principle, which is simultaneously utterly transcendant and also immanent.
Therefore metaphysical knowledge is not human knowledge.
Metaphysics is also important because 'simple' faith is becoming increasingly rare. In bygone days when people lived within relatively closed - cultural and religious - communities, without much interaction with the ’outside world’ (trade was an exception), one was a believer, a follower of a tradition, or a libertine, a scoundrel, or maybe a secret atheist, but one was not confused and uncertain about what to believe and how to behave, at least not to the degree that so many are today. …
If more than one religion is true, then no religion can be absolute - but the essential rationale for any religion is just this: that it gives access to Absolute Truth.
So here would emerge a problem, and this is why metaphysical knowledge is necessary for people who would be in need of it. When religious relativism, ignorance and atheism have destroyed faith, nothing but metaphysical understanding can restore it, if Allah wills so.
Adapted from 'SAC77' - The System Of Antichrist; Charles Upton, p.77
However, in a world where metaphysical knowledge is suppressed, everything is placed on the same value-level; the most wholesome and the most destructive beliefs or cultural manifestations are supposed to have an equal right to exist, simply because they are there.
This is the position of postmodernism and the only thing the postmodernists seem to fear is the tyranny of uniformity where one dominant culture takes over everything and suppresses all minority cultures and beliefs.
This, of course, is exactly what is happening in the world today, as postmodernism is part of the problem (the fitna) and it is profoundly destructive. SAC74
Immersion into metaphysics necessarily entails immersion into the content of revelation.