Some social media platforms are banned in Iran and you cannot access them without a VPN (Virtual Private Network).
You cannot access Facebook, Facebook Messenger, Twitter, YouTube or Pinterest. You can access Instagram, but the rest only with a VPN.
Make sure you download your VPN before you arrive in Iran, because a lot of the VPN sites are blocked by the government.
If you can, we also recommend having access to a few different VPNs, because every now and then one might be blocked in Iran.