  M. Gromov introduced the mean dimension for a continuous map in the late
1990's, which is an invariant under topological conjugacy. On the other hand,
the notion of metric mean dimension for a dynamical system was introduced by
Lindenstrauss and Weiss in 2000 and this refines the topological entropy for
dynamical systems with infinite topological entropy. In this paper we will show
if $N$ is a $n$ dimensional compact riemannian manifold then, for any $a\in
[0,n]$, the set consisting of continuous maps with metric mean dimension equal
to $a$ is dense in $C^{0}(N)$ and for $a=n$ this set is residual. Furthermore,
we prove some results related to existence and density of continuous maps on
Cantor sets with positive metric mean dimension and on product spaces with
positive mean dimension.
