What should you say, as the groom? At weddings I've been at, usually the groom just says a bunch of "I do"s and some vows the fiancees maybe sat down and tweaked from examples they both liked. Then usually at the reception they'll tell a story about how they met, what they love about the other person, and/or what they were thinking or feeling at important points in their relationship. Whoever gives that speech second thanks everyone for coming.

Typically it's the officiant's job to give the speech about what Love is and also about how marriage is hard, and the best man and woman's job to tell the audience how well the couple fit each other while also making fun of them.

I think this is a pretty sensible way to do things. So I'll give you three thoughts:

Option one, the lazy but totally fine way, is you ask your officiant to put the Ursula LeGuin quote (picked as the example because I really like it) in their short speech about what Love is and how marriage is hard.

Option two is to put it at the absolute start of your reception speech - "Ursula LeGuin said "[quote]." With [partner name,] I really feel [feelings that relate to quote]. When I first met her, my first thought was [humorous anecdote]. [rest of speech]"

Option three is to put it at the very end of your reception speech. "[speech, e.g. about a phone call with your mom during which you realized it was getting serious]. The next day I started shopping for a ring. Ursula LeGuin said "[quote]." [Partner name], I [way of pledging your love that uses pieces of the quote]. [Telling them you love them 0-2 more times and ways.]"

I'm tipsy and on a train, so I shall help you

sit down at a computer
open a blank document

call to mind your beloved
bring into your heart the way they make you feel

and then just type a stream of conciousness
tell the bouncer of your mind to take a break
and just type words, they don't have to make any sense at all
and just keep going

if you follow that vein down, you'll strike on high-minded sentiments worth sharing at a wedding

Expertps from things I've squiriled away under "marriage and relationships" that might be relevant to others

• "loving someone is creating a context for their growth, fostering a deep well of reciprocal good will"
• https://xkcd.com/2386/
• "Relationship advice from my wise nonna. Deeply in love with husband for 60 years. After he came back from the war he was suffering from PTSD, he needed a lot of support. But she knew that they still had shared values and dreams, and she clung on to that, and nursed him back to health. This shows we can connect with people at a deeper level, not just the surface behaviour.
• https://www.lesswrong.com/posts/PySEyxTKh5hzDeK9y/my-marriage-vows
• "I swear
  Whatever aid you ask of me, I shall render it
  Whoever you ask me to be, I shall endeavour to become"
• "this seems very new to you
  but seeing someone you like and building a life with them is as old as the seasons changing
  humans arn't as good at it as we used to be, because we need each other less
  but this hides the fact that we still desperately need other people, people who will be close with us
  your branches have intertwined, and if you're brave and determined they will grow
  you will grow so tall, and so vast, and the branches of your love will hold so much
  they will hold your long lives, they will hold the lives of your children the lives of your friends"

Maybe not what you're looking for, but I greatly enjoyed having a Quaker unprogrammed wedding. The format is that everyone sits in the same room for roughly an hour, and when someone (including any of the guests) feels moved to speak about the couple or marriage in general, they stand up and speak. It's very warm and meaningful, and conveniently doesn't require you to provide any content except for your vows at the end :-)

Typically these weddings would not have an officiant, but if you need one for legal reasons or because you've already asked somebody, you can have them step in when you do the vows.

Keep your speech short. Briefly praise people who are there. Other than that, no-one cares. 

An excessive pre-occupation with the wedding is a huge risk factor for a short marriage.

I really like the Finnish gov't notary's speech when they wed people (thanks @Optuses from the ACX discord):

"The purpose of marriage is to create a family for the common good of its members and for the preservation of society. Marriage is intended to be permanent, so that the members of the family may together create a happy home."

"In the presence of these witnesses, I ask you [name]: Do you take this [name] to be your spouse, to love him or her for better or for worse?"

(Answer: I do.)

"In the presence of these witnesses, I ask you [name]: Do you take this [name] to be your spouse, to love him for better or for worse?"

(Answer: I do.)

"Having thus answered in the affirmative, each of you, to the question put to you, I pronounce you spouses."

"In token of your union, take a ring from your spouse." (This sentence is omitted if no ring is given.)

"You are now joined in matrimony. As spouses, you are equal. In marriage, show each other love and mutual trust and work together for the good of the family."

Translated with www.DeepL.com/Translator (free version)