Use of metrics in Models

recently I've been testing use of models.
When I work with simple tables, I have a list of defined metrics (as Administrator) with the right calculations
(count if, case when or whatever). I think it's easyer for users to pick up a metric than knowing wichi filters they have to applay to get the right value (For example: Nomber of visitis is countif(Present=1 and tiquet=1))

But with models... there's no metrics predefined option? they don't work?
then, wich is the difference of working with models or having the tables related by administration->metadata of table?

no one?
Now I need metrics to be built considering related tables... is that possible? without having all the information at the same table?