Unfortunately, there are always exceptions to the masculine/feminine rule, such as

el, la, los , las

Explanation:

There are definite articles that are needed when you are referring to something in spanish.

Words are either masculine (masculino) or feminine (feminino) and usually you're able to tell if something is feminine if it ends is "a" or "as" , however this doesnt work all of the time so study the words and their definite articles so you know what to use :)

Ex.

la computadora ( the computer )- feminine

el reloj ( the clock ) - masculine

Hope this helped! <3