yes we can message someone on YouTube. First of all check whether that person, has a YouTube channel to message him/her. To message someone on YouTube, click on their name (to visit the channel). I’m showing the way to contact right from mobile phone.

Once you visit channel home page, you will see about section as shown in the below image.

Here you will find the information to contact that particular channel owner (some may not provide contact info here). You may find the way to message through email id or their social profiles.

If you want some more information  about how to message someone on YouTube, there is a best answer on how to contact YouTube channel owner.

If you saw that person’s comment, you can reply them with your contact info, so that they may message you.