PMATCH_MP_TAC : thm_tactic
Reduces the goal using a supplied implication, with matching.
When applied to a theorem of the form
   A' |- ! s ==> !q1...qm. t
PMATCH_MP_TAC produces a tactic that reduces a goal whose conclusion t' is a substitution and/or type instance of t to the corresponding instance of s. Any variables free in s but not in t will be existentially quantified in the resulting subgoal:
     A ?- !u1...ui. t'
  ======================  PMATCH_MP_TAC (A' |- ! s ==> !q1...qm. t)
     A ?- ?w1...wp. s'
where w1, ..., wp are (type instances of) those pairs among p1, ..., pn having variables that do not occur free in t. Note that this is not a valid tactic unless A' is a subset of A.
Fails unless the theorem is an (optionally paired universally quantified) implication whose consequent can be instantiated to match the goal. The generalized pairs u1, ..., ui must occur in s' in order for the conclusion t of the supplied theorem to match t'.
HOL  Kananaskis-14