It helps but isn't necessary. I took a year worth of electrical training which helped me but there's some guys that came in with nothing except a decent work history. To get into the one I'm in, I had to pass a basic exam with math, english, and some mechanical questions and pass the interview. They take the score from both of those, average them out and put the applicants into tiers, with the top tiers being hired first and so on. But it really depends on which union you apply for, some have more work than others at any given time...it fluctuates.