Hydrogen ions (H+) are acidic in nature and will readily combine with bases or alkaline substances to form water (H2O) and a salt.

Here's a breakdown:

* Bases contain hydroxide ions (OH-), which readily react with hydrogen ions to form water. This is the fundamental basis of acid-base neutralization.

* Alkaline substances are similar to bases but may not contain hydroxide ions directly. They can still react with hydrogen ions to produce water and a salt.

Example:

* Hydrochloric acid (HCl) is a strong acid, meaning it readily releases hydrogen ions. When it reacts with sodium hydroxide (NaOH), a strong base, it forms water (H2O) and sodium chloride (NaCl) - salt:

```

HCl (aq) + NaOH (aq) → H2O (l) + NaCl (aq)

```

In summary:

* Bases and alkaline substances are the most common substances that readily combine with hydrogen ions.

* This reaction is a fundamental concept in chemistry known as acid-base neutralization.

* The product of this reaction is always water and a salt.