Acid and metallic oxide combine to produce _______________.

When an acid and metallic oxide reacts it produces salt and water. A typical formula for the reaction of metal oxide and acid is,

Metal oxide + Acid $\to$ Salt + Water.

For example,

$\mathrm{MgO} + 2\mathrm{HCl} \to {\mathrm{MgCl}}_2 + {\mathrm{H}}_2\mathrm{O}$

In the above reaction, MgO is the metal oxide that reacts with HCl acid that yields the products such as Magnesium chloride and water.