QC samples resources

I am doing untargeted metabolomics. I have data for HCV patients in different stages of treatment and healthy samples. my data is .raw and I have converted it to mZml files. but, I don’t have QC samples. What is the meaning of QC samples? How can I get it? Can I use QC samples in tutorials? Are QC samples required and must? I am using metaboanalystR as my data size is 180 GB