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I thought it is just me, but when I searched it on Google, it revealed that there are many people who experience this:

Why is it that whenever I taste my own blood, I always think it tastes like rust? I have never eaten or tasted rust, so how can I relate something to it?

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    $\begingroup$ Perhaps iron of haemoglobin makes it taste like rust $\endgroup$
    – Aneek
    Commented Sep 11, 2015 at 16:07
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    $\begingroup$ Related answer $\endgroup$
    – user7951
    Commented Sep 11, 2015 at 17:30

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What you are calling "taste" is actually produced by the olfactory sense – "smell." True taste, which requires contact of a substance with your tongue, is limited to sensations of sweetness, sourness, saltiness, bitterness, and umami. The chemistry of taste is certainly quite interesting, but anything beyond those "flavors" is produced by smell (via far more complex physiological processes). You have certainly smelled rust (or, more accurately, various oxidation states of iron that exist in blood, likely from wet or weathered steel). So you are, in fact, correctly associating the smell of iron oxides from two different sources: steel and hemoglobin.

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    $\begingroup$ There is evidence that metallic taste might be caused by galvanic reactions or even specific receptors in the oral cavity. But I am not sure if this has already been proven in some way. $\endgroup$
    – AstronAUT
    Commented Sep 17, 2015 at 15:46
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    $\begingroup$ @AstronAUT: Good point. I should clarify that my answer does not mean metals have no taste in the formal sense. (A common trick to try to distinguish taste from smell is to simply hold your nose closed while tasting a substance. It's not perfect, because it doesn't seal the nasal cavity, but it certainly reduces circulation of the substance past olfactory receptors.) $\endgroup$
    – feetwet
    Commented Sep 17, 2015 at 15:55

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