Pros
A large company with a lot of flexibility and movement for their employees - you can move around from area to area as long as you make it known to your superiors that you are interested in doing so. Most managers are willing to accommodate your requests provided you are in good standing. Management does genuinely seem like they are interested in your professional development and will help you get to your goals. Of course, some managers are better than others, but you can say that about every company.
Cons
ArcelorMittal needs to evolve with the times and work on educating the bargaining unit employees that they can't go on using the same verbiage/language like they always have been because a lot of it is offensive, even if they don't mean it that way. Also, ratings system can be very unfair to people who have screwed up in the past but have become better employees later on in their career.