What is usually taught first to beginners is the present simple/present continuous difference.
The two verb tenses are contrasted:
- I always eat sausages for Saturday lunch.
- I'm eating sausages now.
But, can I also say this:
- I'm always eating sausages on weekends, instead of any vegetables.
Answer: Yes, please read on.
Generally, the adverbs: sometimes, always, never, usually, frequently, rarely, seldom, hardly, hardly ever [and other adverbs of frequency] are, when in the present, very often in the present simple for general statements.
Then, later, when a student is more advanced*, they can learn that the present continuous + always/never/usually is a kind of special case [Normally, sometimes is not used with a continuous tense, though, it too can be used as a continuous].
- "I'm never doing sports at 7:00 am, like you are implying, John".
- "At three p.m. I'm always finding that my colleagues are falling asleep at their desks."
- "I'm hardly ever searching for lost dogs during the week, but I do do that on weekends".
- "He's sometimes going right up to the referee and complaining to him directly".
Language learning is done in stages, you can't learn everything at once. Generally, in spoken language, people will use the present continuous to emphasize some activity that is repetitive in nature when referring to it in a conversation with someome:
Mother to son: "I'm always finding your dirty socks in the middle of the living room in the morning. That's unacceptable, Johnny."
Could this mother have said: "I always find your dirty socks [etc.]"? Yes, she could have, but as this is habitual or repetitive, and she is speaking to her son, she uses the continuous.
Here is a useful trick you can use:
Please note: The use of the continuous is not restricted to negative statements. It involves some activity that is repetitive in nature and the repetitive quality of which is best served by a continuous, especially, in spoken language, or where a general truth (Dogs play outdoors all the time.) is not the main point being expressed: the main point is the repetitive nature of activity (The dogs at this shelter are always playing outdoors)