The first time I was on chemo 10 years ago, I had that problem too. For some reason plain water tasted metallic to me, but I found by adding flavoring to it, such as a squeeze of lemon, helped. I also could not eat red meat or chocolate, they also tasted metallic to me at the time. I was pretty much on a bland diet during that time, not only because a lot of foods didn't taste that good, but because I had a lot of nausea.
One thing that helped was something my oncology nurse told me; to eat with plastic utensils instead of regular silverware, believe it or not, it helped! And a few weeks after I was done with the chemo, my taste buds returned to normal.
Chemo is not easy for many reasons. If you need to buddy, I am here for you!
I had to go back on chemo 3 years ago and I am still on it, but this time around, my taste buds seem to be normal so far.