"Whenever you cast that spell you may apply any one
metamagic feat you have to that spell without affecting its
level or casting time, as long as the total modified level
of the spell does not use a spell slot above 9th level."
As I understand I can apply 1 metamagic feat, say quickened hold monster, and it will still be a level 5 spell, and I havent violated the rule of being above spell level 9th.
Can I then apply another metamagic feat to the spell, say persistent, and cast as a 7th lvl spell as a full round action?