There is none.

A meaning or purpose implies that there is a controlling being with an agenda. There is no evidence for that.

Like a storm or a fire, life is a process that continues as long as conditions allow.
. .

Everything is both real and unreal. An object is real in the sense that it exists, but it is also unreal because we only experience it through our own perspective, and what we experience might be different to what someone else experiences.

The process of science is such that all theories generated by the scientific method are "provisional"... That is, they hold until better evidence comes along.
So it's entirely possible for a given item of study to be "proven" enough to generate a theory, and then to be found that the basic ideas of the theory were unsound.
In which case it has to be abandoned or at least altered.

Science gradually refines things. Even mistakes add to the body of knowledge.

Kind of depends what you mean by "metaphysics". In more classical use, the term meant simply "beyond physics", and was to deal with things not applicable to the scientific method. The purpose of existence, the quality of human nature....Things like that.

However.... In more recent use, metaphysics tends to be used to describe a great deal of things we skeptics might call "woo".....Things like reincarnation and "higher consciousness" and astral travel and all those other related things that are little more than fanciful nonsense.

One of my favorite quotes of all times concerns metaphysics:

"Metaphysics is like a man without a lamp, descending into a dark basement to look for a black cat....That isn't there."