My neighbour's always popping in for a coffee, which is nice.Although we usually use the present simple with adverbs of frequency, it is possible to use always and words with a similar meaning with the present continuous. The present simple focuses on how regularly something happens and the present continuous emphasises that it happens a lot. It is a way of exaggerating 'very often'. Compare:
She always smiles when she greets a client. [every time that she greets a client]
She's always smiling. [she smiles a lot; not all the time of course]
We can use it when we think something happens too often or we are unhappy about something:
I'm always losing my keys!
You're always talking on the phone when you should be working!
He's constantly playing with his pen during meetings!
She's forever talking about her children - it's so boring!
My neighbour's always popping in for a coffee, which is nice.
My children are always fighting; what shall I do?
We usually avoid using the present continuous (and other continuous tenses) with stative verbs. These are different from active verbs because they describe a state, feelings or emotions. They are also used to refer to the senses or to talk about weights and measurements etc.
I know a lot of Japanese people. [not 'I'm knowing']
He believes in God. [not 'He's believing']
I'm a teacher. [not 'I'm being']
It weighs 3kg. [not 'It's weighing]
However, there are exceptions. See stative and active verbs for more detail.
Verbs like taste, see, hear, smell, sound etc. are more commonly used with simple tenses:
It tastes delicious.
It smells good.
It sounds lovely.
It feels soft.
It looks wonderful.
However we can also use the continuous when talking about current situations:
You look nice today. = You're looking nice today
Do you feel better today? = Are you feeling better today?
The garden is looking lovely now that spring is here.
It is feeling much softer now I have washed it with Lenor.
In informal, spoken English, we sometimes use the present simple and present continuous to tell a joke or relate something that happened in the past because it sounds more interesting or dramatic:
You won't believe what happened last night! Well, I'm cooking the dinner when his car screeches to a halt and I stop what I'm doing. He comes in and he's holding a bunch of flowers. Well, I know what he's thinking...
A dog walks into a bar and he's wearing a suit and tie. He's carrying a briefcase and he says to the barman...