There are two ways to use the three Deco "pods". You can use the three of them as repeaters for your current router, which is connected to a modem, but most people use the three to set up a wifi mesh network. The latter method also requires a modem (through a service provider - Optimum, Comcast, Verizon, etc). The Deco pod connected to the modem acts as the main router with the other two acting as extenders. However, when all three are connected together, you only see one wifi network on your device to choose from, as the pod closest to your laptop, phone, tablet, etc will provide the signal. I realize this is a long answer to a short question, but I hope this helps. BTW: It took me less than 30 minutes to connect all three Deco pods on three different levels of my house. It couldn't have been easier, and the wifi signal is strong in all corners of my house.
If your entire network is under the metal roof, there should be no problem. If you are trying to pass a wifi signal through a metal roof, then no wifi router will help. However, because there a three "pods", if you have to get around a metal roof, you can place one pod in a location that is "seen" by the "pod" on the other side of the roof (if that is possible), pretty much reflecting the signal around, not through, the roof. Hope this helps..
Yes it can, or you can use the three as extenders if you really like you present router. Most people use the three Deco "pods" to replace their current router and extenders.
My download speed is consistently around 113 Mbps, upload at around 37 Mbps. A lot depends on your service provider.