otaku_emmy said:

Anyway, I was just wondering. I never understood how he could withstand so much physical damage.
Oh, that's an easy question. :)

Michael Myers is a metaphor for evil in all its various forms. Evil never truly dies.

EDIT: Reading your comment again, I might need to elaborate on my answer. At first, I believed that you were referring to Myers’ frequent resurrections after being taken down. Now, it has occurred to me that you could be questioning how he can actually receive critical physical damage and remain upright.

The truth is, there is no definitive answer as to why he has superhuman strength. However...

According to John Carpenter, he originally envisioned Michael Myers as a malevolent force of nature, akin to a firestorm or hurricane. The literal embodiment of murderous intent.

In Halloween (the first film, not the franchise), evil is not merely a concept, but a fundamental element – like wind, rain, or thunder. Because Myers himself is a metaphor, this explanation makes the most sense to me.

Another theory concerns Myers’ psychological state.

Due to his complete lack of empathy and hatred for those around him, he can channel his aggression into his murderous acts. Myers might react to receiving a knife in his shoulder, or a gunshot to the chest, but that doesn’t necessarily mean he would feel it. Because he has no emotion. And, hate... well, it can sometimes be a great motivator. This could enhance his strength.

Strictly speaking, Myers is a precursor to the T-800.

And, there is the so-called Curse of the Thorn, a nonsensical conceit introduced in one of the latter Halloween films. (Halloween 5?)

After a ceremony by the Thorn Cult, Michael Myers obtains inhuman strength, stamina, durability, immortality, and the overwhelming pathological desire to wipe out his entire family bloodline. Personally, this is where I dropped out from watching the rest of the franchise...

Whew. So much for a short answer. :)