Convergence of sequences in D' is not metrizable

Question

I'm struggled with the problem. I need to proove that the convergence of the sequence of generalized functions in D' can't be defined by any metric (can't be metrizable). I've tried to use the fact that the sequence convergence in D is not metrizable. And then to prove by contradiction. But i failed and was told that it's the wrong way to do it. I'll appreciate any help or materials which can help me.