I came across a sentence in scientificamerican
Summer’s here and with it come picnics, barbecues and of course Salmonella.
Why not comes but come? I found there are
Here Comes the Boom. Here comes the sun.
When to use come and when the other?
It's because picnics and barbecues is plural.
Picnics come in the summer, the sun comes at dawn.
When the noun is singular, we conjugate with comes; when the noun is plural, we conjugate with come.
The examples which you have given are present indefinite. In present indefinite, we use a verb’s first form. If the subject is singular the verb comes with ‘s’, and if the subject is plural only the verb’s first form is used.