Metal Storage is a type of Production Building which increases the amount of Metal that the town can store. You can build up to 6 Metal Storage.
The town's initial metal storage capacity is 4000 units. Once maximum storage is reached, no more metal can be harvested. The game will leave any remainder in the Mine.
Building/Upgrading[]
To build Metal Storage, players must first acquire the Metal Storage artifact.
* assuming that Rally isn't used to speed up building
Upgrading advice[]
Looking at storage/price ratio, Rank 3 is more convenient than Rank 1, that is more convenient than Rank 2. So if you need a very large amount of additional storage, it's better to upgrade to Rank 3.