The answer to this question will depend on a few factors:
Which blood is being described.
Who is doing the describing.
How fancy you want to get.
So, if you’re talking regular ole human blood, that’s one thing, but alien blood could smell like anything. It might smell like butter or clams or books. You can make that up. Also, there are a few taboos with describing human blood that you wouldn’t have to worry about when describing animal blood, especially if the animal blood is somehow food, as in a rare steak or blood pudding.
If you really are just trying to describe human blood, however, I’m going to give you some words to use, but you’ll have to wait until the end of the post. I promise they’re there. Keep reading.
Who is doing the describing is also important. Vampires, for example, might describe the smell of blood much differently than a regular human. They might say it’s sweet-smelling or intoxicating or rotten (ew, gross, werewolves… or something). Since, at least for many vampires in fiction, blood is all they eat and their sense of smell is attuned to differences in blood, they’d have a much larger (and probably creepier) vocabulary for describing the smell.
However, vampires and other blood-guzzling monsters aren’t the only ones who might describe the scent of blood differently than normal people (nothing against any vampires who might be reading). There are smell and taste disorders that might cause a person to describe blood differently than others.
Dysosmia, for example, is “a neurological disorder that causes an altered sense of smell. The condition can manifest itself in a variety of ways: it may distort smells, which is a sub-condition called parosmia; initiate no olfactory response at all, called anosmia; or produce smells that aren’t there, called phantosmia.” (x)
Without a doubt, someone with Dysosmia is going to smell differently than you smell. For ideas, I’d find someone with Dysosmia and talk to them about their disorder. There are also a few links to learn more about this condition in the resources section below.
People with a fear of blood, known as Hemophobia, might describe blood differently. How their fear affects their descriptions is up to you, but attaching fear to a smell is bound to change a person’s descriptions of said smell.
Then there are cannibals: people who eat other people. To them, blood is a part of food, and food gets different boundaries on descriptors than human blood. Describing human blood as delicious or mouth-watering might get weird for the non-cannibals in the room. And, not to compare them to cannibals in any other respect, but this is also a problem for blood fetishists, people who derive sexual pleasure from blood. The sexualized descriptors they might use don’t fit neatly into society’s acceptable vocabulary for describing blood either.
Now that we’ve covered why a character might describe blood differently than others, let’s talk about how fancy you want to get.
It’s pretty common to hear blood described as metallic. That’ll be on the vocabulary list at the end of the post, for sure. But there are other ways to describe metallic smells, aren’t there, and ones that might help ground the description in setting or character. Let’s explore a few examples:
His blood smelled like my grandfather’s old change jar that he kept in the window of his study. The morning sun hit that jar and by lunchtime the whole room would smell like metal. It made me sick. I couldn’t even go in to borrow a pen unless the sun had been down for hours.
His blood smelled like a smithy, like raw iron and earth.
His blood smelled like the kitchen sink after Mother had cleaned the pots and pans with her metal scouring pad.
Metaphors might help you ground your descriptions more firmly into your story, but first you’ll need some basic springboard words. Here, finally, is a list of smells associated with fresh blood:
metallic
coppery
like iron
rusty
minerally
tinny
ruddy
like wet metal
like pennies
salty
musty
heady
The older wet blood is, the sweet it smells. Some people would even describe it as fruity, nutty, or ripe. Dry blood might smell mustier or more rancid than wet blood. Smell is also very closely tied to taste. Trying to get a handle on how you think blood tastes might help you describe its smell.
Keep in mind that human experience varies widely. Some people can’t smell blood at all, and others can smell a bottle cap’s worth of blood in a large room. Sensitivity to the smell of blood depends on the person.