Honey, I am at home!
Because home isn’t a normal location, it’s “home”.
It’s where you’re from.
Like, no one says “I’m house” or “I’m apartment building” because it’s not about the physical structure. It’s about being where the heart is. How many pillows do Grandmas need to stitch that on?
In this usage, “home” is an adverb / adverbial! It is a preposition being used adverbially.
I’m going in. I’m going home.
Send it out. Send it home.
Run away! Run home!
If home is where your heart is, and I have my honey’s heart, then saying “Honey, I’m home!” makes perfect sense.
You’re thinking in terms of location, rather than state-of-being. “I’m home” is your status.
“I’m driving, I am bored, I’m safe, I am away”… None of those sound weird, do they? This, combined with the more technical grammar rules others have commented…
Home is the adjective. It’s a state of being.
Many times I’ll walk in the door but need to log into work, and I’ll say to my wife “I’m not home yet”. As in, my external responsibilities are not completed and I am not available. When I’m available to my family or to relax, I have then become “home”.
Edit: I meant adverb. It modified the state of being. Like being “away”.
