When people refer to men as "mate" or "pal", Liverpool people often use the word "lad" in the same way. An old workmate of mine who originated from Lancaster, but worked in Liverpool once said to me that if he called unknown people in the pub or wherever "mate" that would be fine, but if he called them "lad" the response would likely be, "Eh, who are you calling lad?" with the possibility the question being followed by a thump.
I know it is just a local phrase and if a stranger refers to me as lad I have no problem, but listening to some young scousers talking to their mates these days, every few words are punctuated by the word "lad", there is no way you would ever use a person's name with such frequency, it is cringeworthy.