Plagiarism isn’t allowed but quoting clever people is.
You’ll know the right quote when you read it; you’ll get that spark of recognition, that ‘blooming hell, I didn’t realise other people felt that too’.
Quotes are a great way of nailing the romantic bit of your speech without it being cringey or cheesy. Let other people take the blame for being poetic. It’s also a legitimate way of adding guaranteed humour to your speech so tuck in and exploit them.