When Orsino speaks about his love for Olivia, his speeches are grandiose and filled with hyperbole and figurative language. This language, which is often clichéd and insincere, emphasizes that Orsino does not actually love Olivia and is in fact more obsessed with the concept of being in love than he is with any individual woman.
During an exchange with Curio in Act 1, Scene 1, Orsino uses a particularly flamboyant combination of metaphor and hyperbole:
Orsino: O, when mine eyes did see Olivia first,
Methought she purged the air of pestilence.
That instant was I turned into a hart,
And my desires, like fell and cruel hounds,
E’er since pursue me.
Olivia is obviously not actually a human air purifier, but this hyperbolic statement emphasizes Orsino's unrealistic view of her. Orsino considers Olivia so pure and chaste that he views her as incapable of producing body odor and regards her very presence as purging the air of unpleasant scents. In other words, he does not view her as a human being.
Orsino's use of hunting as a metaphor for love—comparing himself to a deer and his desires to hounds in pursuit—also illustrates that he is more interested in the pursuit of love than he is in Olivia herself.