You're right that none of the transition metal atoms have an overall charge. In fact this is true of all atoms!

An atom is made up of 3 kinds of particles:
electrons (which are negatively charged), protons (which are positively charged) and neutrons (which don't have a charge).

In an atom, there is always the same number of electrons as protons, so overall there isn't an excess of positive or negative charge.

It's not possible to change the number of protons in an atom easily (in fact when one does this, one changes the atom into another kind of element!), but it's possible to add or subtract electrons to form what we call ions.

If you add electrons you make a negatively charged ion (called an anion); if you remove electrons your ion is positively charged (called a cation).

Transition metal atoms are quite good at giving up electrons, and so they can form positively charged cations. But in the atomic state they are always neutral.