Metals that donate electrons become positive ions, meaning they attract and stick to negative ions (atoms which have gained electrons).
Electrons are little negative particles you find around the atom. There are normally the same number of protons and electrons, which means there is no overall charge, except in ions.
Ions are when an atom has gained or lost electrons, and so has a positive or negative net charge.
Usually, for example, if you had
If a metal donates (gives away) electrons, it loses negative charge, so becomes less negative. Less negative is the same as more positive, because they are simply opposites. Therefore, a metal donating electrons becomes a positive ion.
If it donates
Positive ions can also be called cations, and negative ions are anions.