Although at face value could be conceived to be a leet version of the word "true" (which it is in one sense), it is actually more commonly used amongst fans of black metal, particularly of Scandinavian origin, to compliment a band, person, or thing for it's black metal or Nordic/Viking values.
It's origins are not certain, although one theory suggests it comes from an old polytheistic religion of Northern Europe called Ásatrú. In early days, old Norse languages had no word for "faith" or "belief". Instead they used the word "tru" or "tro" meaning "truth" or "loyal to".
So using the word "tr00" in black metal terms in this case would mean black metal that is honest, genuine loyal to black metal ideas and customs.
The word does not necessarily have to be applied to bands or people, in some cases, with the more cultured and perhaps slightly more tongue-in-cheek, might describe a place as tr00 for its Nordic, satanic, spooky or dark vibes.
The term kvlt may also be used and has a similar effect.

From STEM, an abbreviation short for "Science, Technology, Engineering and Mathematics", a STEMlord is a pejorative term for a particular kind of person who has studied in these areas at university or works in these fields who holds a pretentious, condescending attitude to anyone who has studied in any other fields, particularly the Arts and Humanities. They typically believe themselves to be more "intelligent" and "rational", while generally remaining incredibly ignorant outside of their areas of expertise and having the charisma of a rotting pig's backside.

ADJ: see true. can be used to agree with any statement, or to express a common interest.