Some devices might have security measures in place to help protect them from getting infected, but if your device is compromised by malware it may do some of the following:
Slow Down: Malware can slow down a device's performance. For example, if it's on edge and making lots of requests to the internet, a virus might slow down the computer so that it can't keep up.
Lose Data:Malware can delete data or encrypt files on your device. This means you may not be able to access your documents or applications.
Make It Easier For Someone Else To Access Your Device: Malware can make your device easier for someone else to access - like a hacker. Viruses might allow hackers into your computer through ransomware, which locks users out of their devices until they pay money to the hacker.