My bf has diagnosis of metastatic liver cancer. how long does he have to live?

Depends: Liver cancer that has moved to other organs often has a short overall survival. That being said, there are exceptions. To find out more, ask your doctor how long between the time the liver cancer and the metastasis was diagnosed, how many metastatic sites are there, and how large are they. These pieces of information will help answer your question better. Sometimes isolated mets can be removed.

Usually short...but: Some lesions can be resected, ablated (burnt) or combinations of these modalities. These, coupled with chemotherapy, can be curative in selected patients in up to 40% of cases.