Basic Points

• An ITM (in the money) option always has some intrinsic value. 
• Intrinsic value is a guaranteed part of the option’s price, depending entirely on whether the underlying security’s price is beating the strike price (the target price which the option is based on). 
• The intrinsic value of an ITM option stands regardless of time remaining or implied volatility (a demand-related premium for that option).  
• One quick way to confirm if an option is ITM is to check that its delta (measure of directional risk) is significantly greater than 50. 

Advanced: Dynamics

The main reason investors will buy ITM is because they are a relatively stable form of leverage, which is a way to tie up less capital in representation of a larger (and more dangerous) position. 

Buying an ITM option is defensive compared to trading at-the-money (roughly 50 delta) or out-of-the-money (roughly less than 50 delta). However, an ITM option misses much of the magic of what makes something an option because it will have less gamma, which is the curvature and rate of change of delta per underlying movement. We can refer to this long gamma property as magic, so to say, because that long gamma will reduce size as you become increasingly wrong about direction, and increase size as you become increasingly right about direction. 

Another downside of buying and holding ITM options is that they cost more, which means they have more absolute risk. It is also a fact that deep ITM options tend to be much less liquid than at-the-money or out-of-the-money options, which means that there is a greater bid/ask spread (extra money lost from trading due to how great the distance is between bid and ask).