The short answer
If your artwork is flat colours and a logo, use Pantone. If it has a photograph, an illustration with blends, or a gradient, you need CMYK.
You can have both on the same tin. A CMYK image with a Pantone brand colour over it is a normal thing to print.
Why Pantone is sharper
Because the colour arrives already mixed. One ink, one screen, one solid area of exactly the colour you picked. Edges stay crisp and a flat area stays genuinely flat.
It also repeats. The same Pantone reference next year gives you the same colour, which matters when a customer sees your pack next to last year is on a shelf.
Why CMYK is more flexible
Because four inks build anything. Cyan, magenta, yellow and black, screened together, will reproduce a photograph or a gradient that no single mixed ink can.
The trade is that a solid area made of four screens is never quite as flat as one made of one ink, and very fine type in a build of four can lose its edge.
The white base coat, and why it matters
Tinplate is not white. Ink printed straight onto it picks up the metal underneath and shifts, which is why almost everything goes down over a white base coat first.
That base coat is also why a Pantone on metal and the same Pantone on a carton will never be an exact visual match. If your tin sits inside a printed box, we proof both together rather than trusting the reference number.
What to send us
Vector artwork if you have it, with Pantone references named rather than described. If your artwork is a photograph or has blends in it, just tell us and it goes CMYK.
Either way you get a proof printed on tinplate before anything runs, because a screen has never once been an honest preview of ink on metal.
Hold one before
you specify it.
Tell us what you're packing and we'll send the formats that suit it.