One of the things to look out for when picking a VPN is leak protection. It's the reason that using the best VPN for China has become so popular and useful, allowing those located there (either permanently or temporarily) to get around websites otherwise blocked by the government. Most VPN provides don't keep data on users meaning that your assigned IP shouldn't be linked to your physical address anyway – keeping you secure. Even if someone was somehow able to get to your IP address, it wouldn't actually be yours, but one that's hidden behind the VPN's server. Since a VPN will assign you a new IP address and run your data through different servers, that makes tracking you very, very difficult. We'd love to say it'll keep you safe from all, as we almost feel confident enough to say that, but being realistic we're going to simply say a VPN will make you far safer than you are now. A VPN is way more than a lock but it will certainly keep you safe from most potential threats.
But much like a bike left unlocked might be taken by an opportunist, if it's locked up that stops most people even trying to take it. It's worth keeping in mind that folk say anything can be hacked with enough time and computing power. In the case of ExpressVPN (opens in new tab), for example, data is managed using RAM so it's never actually written onto any drives. Often, in most cases these servers won't store data for a period of time, meaning it's tougher to access.