This is an extremely rare piece (the only one I've ever seen and very likely the only one in anywhere near this big), a bronze kouros. I can unfortunately tell you only very little about the statue, as there is little consensus on the dating and style.
Anyway, the statue is from Piraeus and was found in a burned warehouse with several other impressive bronzes (among them one Athena). It has been argued that the building was destroyed in a fire just before Sulla had time to ship of his booty to Rome, which mean that that piece have to be older than ca 86 BC, but also that it was not lost already at that date.
This may seem good, but it raise a number of problems. First of all, this statue would, by form and style, be dated to ca 525 bc (some 440 years earlier) - could it really have survived that long? Secondly, there are reasons to doubt that it's an archaic piece: the right foot is put forward (almost all other kouroses put their left foot forward), the arms are raised and it seems like he once had something in his left hand. It could very well be a Hellenistic copy or imitation (which would fit in well with the other bronzes from the find spot), but if so, why is this the (to my knowledge) only one preserved?
You can compare it to other kouroses from ca 600, the early 6th century, ca 530 and ca 490-480.