Erlang's main weakness is computationally intensive mathematics. You could always write a NIF in C if you needed pure speed for a specific function. If you're not interested in writing safe c code it looks like there is a bridge from rust to erlang.
> http://erlang.org/doc/tutorial/nif.html
Erlang itself shield you from actually doing stupid thing and follow the assumptions that BEAM have while running programs.
You're better off choosing a different language. Have Erlang deal with concurrency but don't have it do number crunching.