Hi Jo Elise. Welcome to the forum, and I'm so sorry to hear the news about your grandfather.

Metastatic cancer is never good news, however, there are some good treatment options for your grandfather. These will make him much more comfortable, and control the cancer for a good period of time, but at present they're unlikely to cure him. The chances are that you will still have a good few long walks with him in future. 

Hello Jo Elise.  So pleased to have you here at what must a scary and sad time for you.  I was 14 when my maternal grandfather died (suddenly of a heart attack) and it created a big hole in my life.  It was the first person in my family to whom I was close.  He and my nana lived quite close by and I had spent a lot of time with them as I grew up.  It was a big hole in my life when he died. 

You still have the same loving grandfather.  Keep on doing what you have always done, love him, talk with him about the things which interest both of you and whatever other activities you enjoy.  It sounds as though he won't mind you asking him questions about his illness as you have always talked about everything.  Keep it as normal as possible.

And keep posting here, especially if you have really bad days when it is all too much.  We are always happy to chat with you.    Annie xx