It depends on what you are trying to say...
Daniel is ALWAYS missing class.... it means he never comes to class... it �s a negative action always being repeated.
EG: He �s always swearing as opposed to he always swears.
He �s always arriving late
I �m always losing my car keys
She �s always complaining
(I would not say he always misses class in this case however I would say it to highlight the reason..... He always misses his math class in the morning due to heavy traffic)
Daniel always has to miss class... it means there is a reason why he cannot come to class.
He always has to miss class in the afternoons because he is going through medical treatment.
Does that make sense?? :)
Hope that helps x