so is it possible to increase mph by putting a 1000 watt battery on the metro?
Okay, initially I was confused why you let an empty reply, but I'm guessing this is the part you wanted to respond.
You combined my response and your response, that's why it didn't show.
Anyways,
There's no such thing as 1000W battery. Did you mean 1000Wh battery?
Not all 52V battery are 1000Wh, even if it's 400Wh, it has no effect on top speed, as long as the voltage is the same.
(yes, it all depends on other factors like BMS and drain rate as well)
What determines top speed is the voltage, so by going 52V battery, you will increase 2 or 3 mph.
However, if it's electronically restricted by the display, it won't go any faster than 25mph.
You controller will be fine, since 48V controller can generally be able to handle 52V just fine.