As it's your intention to join up as an ME, when alongside you will still be required to carry out much the same tasks as when at sea, i.e. watchkeeping duties, maintenance routines and repair of equipment, oh yeah, never forget the cleaning. When not onboard a ship you will be employed in trade doing similar jobs or away on courses. If you're lucky they might even let you have some leave.
As an AB there is now very few jobs which have specific shore jobs. But there is a system called top mast which is supposed to give you some shore time. Thenas an ME you would probably be employed at SFM. Which is a shore side maintenance team. Where you go off to work on different ships when they are alongside. Doing jobs which are the ships company do not have time to do.
There is also the chance you could go and work with the marines for a tour. Which is becoming much more common. But that wont be until you are qualifed as an ET1