Your phone may still work after a power outage, but it won't help you much if you can't use it to connect to cell service or the internet. It's one of the reasons why investing in additional communication equipment, such as a HAM radio or a CB radio, will be critical. If you are out in the middle of nowhere without any form of communications, then you'll need something that works even when the lights go out.
Most phones have an option known as "offline mode". This lets you use the phone while it connects to various networks to check for messages or calls that need to be made. If there are no connections available, the phone will stop trying to contact other devices until network services are restored. However, this only helps you if you're able to make calls during these periods. If you try to use your phone for email or browsing the web, you won't be able to do so because it requires constant connectivity.
If you lose connection with towers and cell sites, then your phone will switch from using them for navigation or audio streaming to using them for data storage. The more data it has to store, the less responsive it will be when you try to use it. Emails and texts will still arrive at other people, but you won't be able to send or receive new messages until connectivity is restored.
Phones also cache information about websites in order to load them faster when they are next visited.
Here are a few technologies that will assist you in communicating if a calamity happens and the power goes out.
If a utility tower is located near a home or business with a metal roof, your service may be disrupted. When this happens, the radio frequency of a cell phone can be disrupted, but the underlying problem is with the tower, not the metal roof. Cell phones use radio waves to communicate with base stations, and a metal roof can interfere with these signals.
As long as there are no metal panels facing the tower, you should have no problem using your phone's data plan. However, if any metal does face the tower, you'll need to find another place to mount your phone so it doesn't receive its signal from that particular tower.
This issue applies only to metallic-looking roofs. Other types of roofs do not affect cell phone reception.
If you own a business and have a metal roof, you should know about this issue before you hire an architect to design your new office space. If you want to ensure that you can still use your phone's data plan in the area behind your desk, then you will need to find another location for a utility box.
Metal roofs are common in large buildings such as shopping malls and airports, so make sure you tell anyone who asks that your roof is made of metal if you want them to avoid mounting phones or other equipment on top of it.