Men are strange. = Muži jsou zvláštní.
The men are strange. = Ti muži jsou zvláštní. (Those men are strange.)
English "the" is usually translated to mean "that" or "those".
Still, that isn't always true. If I was in a conversation and just said "The men are weird" it couldn't be translated as "Ti muži jsou zvláštní", but if you were like walking down the street seeing some weird guys, you could use "Ti", which would be better translated into those and not the
If I were translating from English to Czech I would only use "ti" here if the sentence were obviously emphasizing particular men and not others. For example, if the English was: "You don't know them. The men are strange": I would use "Muži jsou zvláštní." I would only use "ti" where there is no "those" on rare occasions. At least this is what I learned in former Czech courses and from Czech speakers.