British heavy rock band Saxon had a hit with Princess of the Night. Despite the potential suggestiveness of the title it is a straight tribute to a steam train (delivering mail during the night.)
TCMF-2L
If love between a human and something non-human counts, then there are countless examples (e.g. I Love Rock 'n Roll by Alan Merrill). Or does the OP only want examples of songs about love between two non-humans?
Tom Waits’ “Heart of Saturday Night” is another love song about a car.
“Stick It Out” and “Sy Borg” from Frank Zappa’s “Joe’s Garage” are songs where the singer is getting intimate with kitchen appliances.
“Love me, love my dog” by Pete Shelley, 1975.
Mary had a little lamb
Although the lyrics aren’t explicitly direct, I’m pretty sure Neil Young’s Sample And Hold is about mail order love robots.
Also, does it count if the object of affection was human, but isn’t anymore? “She’s cool in bed – she oughta be, 'cause Ethyl’s dead.”
Donavan - I love my shirt - --------------- and other items of clothing
Do you mean songs about love/affection between two non-humans (like “Muskrat Love”)? Or between a human and a non-human (like “Martha My Dear”)? Or either/both?
Another example of the latter is Queen’s “Delilah,” about Freddy Mercury’s cat.
As long as at least one is non-human anything counts.
Technically not a love song, since he only states that it is “a very good friend of mine”, but David Bowie’s TVC 15 is about a television set.
Another “good friend of mine” was Jeremiah the Bullfrog.
“The Very Last Time” by Alan Parsons was written by guitarist Ian Bairnson to his beloved dog who passed away. It’s a real tear jerker.
Oh, they say she died one winter
When there came a killing frost
And the pony she named Wildfire
Busted down its stall
In a blizzard, he was lost
She ran calling Wildfire
I presume we’re not counting religious songs? There are plenty of songs about love between God and humans.
Be My Girl - The Police - Do inflatable humans count?
Truck Love - a song about somebody who really loves his vehicle.