What Causes Metallic Taste In Mouth?

This morning I woke up feeling pretty normal. I went into the bathroom to and felt like I had excess mucous in my throat, which I usually have in the morning, but I clear my throat and spit a couple times and it s gone. This morning however, I cleared my throat and spit and my spit was bright red and I noticed my mouth tasted metallic. I know the taste of blood and am most certain this was blood. I cleared my throat and spit about 8 more times, each time most of what I spit out appeared to be bright red blood. Around the 9th or 10th times, the spit had become mostly clear. I inspected my mouth for any sign of cuts, scrapes or open wounds and didn t find any. There was no blood between my teeth. I blew my nose and there was no blood from my nose, so I eliminated the possibility that perhaps I had simply had a nose bleed in the night that had run down the back of my throat. What could have caused all this blood in my throat this morning? I don t have a cough, sore throat, trouble breathing, upset stomach or anything that would indicate an internal wound.