This is just one part of the mechanics of mono battles I would like clarification on. Thanks!
Both teams do not have to have the same type. If I used Fire-types and you used Poison-types, it would still be a mono-battle.
Monotypes are basically this. Both teams can be whatever type they want just as long as they have teammates that have the matching type with them.
Charizard Talonflame Chandelure Victini Darmanitan Heatran (Mono Fire)
Politoed Kabutops Kingdra Starmie Gyarados Blastoise (Mono Water)
Pokemon with Dual types do not break any of the Monotype rules whatsoever
The 1st rule of Mono is all of your team "members" must share the same type, the type matchup (which type of team will go against whch type of team) is limitless.
-A Steel team can go against a Poison team.
-A Water team can go against a Grass team.
-A Fighting team can go against a Fighting team.
Source: being a mono pro, yo. (playing alot of Mono on Showdown.)