We have several examples of Hemalurgic spikes being used to control or manipulate a being:
However, Spook's letter in The Hero of Ages reads:
My mind is clouded. A part of me wonders what is real anymore. Yet, one thing seems to press on me again and again. I must tell you something. I don't know if it will matter, but I must say it nonetheless.
The thing we fight is real. I have seen it. It tried to destroy me, and it tried to destroy the people of Urteau. It got control of me through a method I wasn't expecting. Metal. A little sliver of metal piercing my body. With that, it was able to twist my thoughts. It couldn't take complete control of me, like you control the koloss, but it did something similar, I think. Perhaps the piece of metal wasn't big enough. I don't know.
Either way, it appeared to me, taking the form of Kelsier. It did the same thing to the king here in Urteau. It is clever. It is subtle.
Be careful, Vin. Don't trust anyone pierced by metal! Even the smallest bit can taint a man.
The Hero of Ages - Chapter 69
So I'm wondering if this is indeed true. I can only think of one example that would support any metal allowing control or manipulation.
The Lord Ruler said:
I fear that it has corrupted my thoughts. It cannot sense what I think, but it can speak inside of my head. Eight hundred years of this has made it difficult to trust my own mind. Sometimes, I hear the voices, and simply assume that I am mad.
The Hero of Ages - Chapter 48
And in The Final Empire:
[Vin] flared the iron. Blue lines appeared pointing to the Lord Ruler’s rings and bracelets—all of them but the ones on his upper arms, piercing his skin.
The Final Empire - Chapter 38
These bracers obviously were not Hemalurgically charged, because the Lord Ruler had no need for that being a full Mistborn and Feruchemist already. And yet it allowed Ruin to speak to his mind.
So is it truly any metal in a person allows control? If enough coins were shot into someone could they be controlled? What about Miles Hundredlives1? Would Harmony be able to fully control him due to the number of piercings? Could the Lord Ruler have taken control of a Terris Steward2 like he did the Koloss?
In short, does the Metal have to be Hemalurgically charged to control someone?
(all emphasis mine)
1 - Miles Hundredlives
“You need to get [Miles'] metalminds off of ’im,” Wayne said. “It’s the only way.”
“He keeps thirty different ones,” Waxillium said, “all piercing his skin,
The Alloy of Law - Chapter 13
2 - Terris Steward
“You’re a Terrisman,” Vin said. [Sazed's] earlobes had been stretched out, and the ears themselves contained studs that ran around their perimeter. He wore the lavish, colorful robes of a Terris steward
The Final Empire - Chapter 8