I have stayed at Melbourne Metro YHA more than once over the last few years. Cleanliness is always pretty good; the rooms especially (I have always had a private room, but friends I've stayed with have used dorm rooms and these seem clean too), and the beds, while very standard fare, are comfortable enough, again with clean linen, etc. Heating/cooling in any of the rooms I've seen is centrally controlled, but the temperature has been comfortable, and you can open the windows to get some fresh air. Sometimes the shared bathrooms can get a little grotty, but nothing too bad. The showers are pretty good; good pressure, hot, not usually that busy, and a bit of space. The in-hostel restaurant and common areas are also quite clean and accommodating.
I have always found it to be pretty safe as well, both the hostel itself and the surrounding area. I have returned to the hostel late at night on a number of occasions and never felt any concerns walking through the (dimly lit) surrounding streets. You sometimes get some moderately rowdy people staying at the place, but that's typical of any hostel. The rooms also seem secure, although I have had occasional mishaps with the swipe cards malfunctioning and not opening my door; this has always been quickly remedied by the front desk, although note that the desk does seem to close reasonably early.
Possibly the biggest downside is the location, assuming you are wanting to access central Melbourne. It is walkable, but you'd be looking at minimum of 15 to 20 minutes to get anywhere you'd be likely to want to go. The nearest tram stop is only about 5 minutes though, and trams are regular (you can catch any of several tram numbers to and from the city). Most of Melbourne's attractions however would require at least one change of tram to get to. Accessing Southern Cross Station (the main country/interstate station) is also indirect even though it's not that far away. The Queen Vic Markets are close by, easy walking distance and worth visiting. There's not really a lot of eateries, etc in the immediate area; you usually need to travel a bit. Other attractions such as Lygon St, Melbourne Museum, and the Carlton Gardens/Exhibition Buildings are a similar walk as the city, but this is a very doable and quite interesting walk; public transport to these locations is a bit inconvenient though. The Melbourne Zoo is also in the general area.
The rooftop common area gives great views of the city, but doesn't seem to get a lot of use. Is is also locked quite early so that may help explain its lack of use. I'd also say this reflects the point that the Metro isn't really a 'party hostel', so if you're after that scene look elsewhere. In fact it tends to be a little bit lacking in character and is not particularly the type of place you get to know too many other people, although that could also reflect that I've usually stayed there with others and gone out most of the time. The staff are also usually helpful enough, but not overly friendly.
All up this is a clean, safe, and quiet hostel. It's a little out of the way and not overly social, but somewhere you can get a good night's sleep, or can base yourself comfortably to explore Melbourne. I have stayed there more than once and would stay again, but I wouldn't hesitate to try somewhere else either.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC