Q:

How to get monomials multiplied by each other?

Suppose Subscript[x, #] & /@ {1, 3, 7} that returns {x_1,x_3,x_7}. Now how can I get x_1x_3x_7?
Tried it already...

P.s. I am trying to understand this thread deeper about converting binary mlfs to mlfs.

A:

It is due to precedence. Need to use () in this case.
Times @@ (Subscript[x, #] & /@ {1, 3, 7})

See this when-is-fg-not-the-same-as-fg topic for table of precedence in Mathematica.

A:

Two more solutions:
Times @@ Thread@Subscript[x, {1, 3, 7}]

In the notebook it can be written more compactly

The second one shows the behavior of /@
Subscript[x, #] & /@ Unevaluated@Times[1, 3, 7]

