Well it is more similar with FOREX since they are both currency, But if you are already trading stock it will be easier for you to learn how to trade currency. You might already know the basic of trading and if you already know how to read charts it will be a plus for you.

Also you can see right away the  difference on their volatility. In crypto currency trading prices goes up and goes down instantly while on stocks sometimes you need to wait for days and some cases weeks or months to get a decent profit.

In stocks I usually use a daily and weekly view but in crypto currency a weekly view is comparably a year in stock charts.