One of the most convenient features of iOS 11 is the ability to share with a friend or guest access to the Wi-Fi network without entering a password. Both Apple devices must have iOS 11 installed and Bluetooth activated.
On the guest iPhone, open the familiar Wi-Fi connection screen, go to Settings / Wi-Fi, and select the desired wireless network. When the password input window appears on the screen, you just need to swipe it and bring both devices close together.
Just like when creating a pair with AirPods, a window will appear on the devices display asking if the user wants to share the Wi-Fi password. When the "Allow" button is pressed, the password is sent and the guest device is connected to the network. This works not only with the iPhone, but also with the iPad and other Apple devices.
Also, you can set up a new iPhone or HomePod column by simply holding the device next to the already connected iPhone.
This way you can share passwords not only from home, but also from any other network that the iPhone has access to, including connecting to the device itself, which is in modem mode.