The nature of mind is debated. What is the nature of mind? I think there are different perspectives. An untamed defiled mind is like a monkey, grasping this branch and that branch. Such a monkey mind is described in SN12.61. It is unstable.
"It would be better, bhikkhus, for the uninstructed worldling to take as self this body composed of the four great elements rather than the mind. For what reason? Because this body composed of the four great elements is seen standing for one year, for two years, for three, four, five, or ten years, for twenty, thirty, forty, or fifty years, for a hundred years, or even longer. But that which is called ‘mind’ and ‘mentality’ and ‘consciousness’ arises as one thing and ceases as another by day and by night. Just as a monkey roaming through a forest grabs hold of one branch, lets that go and grabs another, then lets that go and grabs still another, so too that which is called ‘mind’ and ‘mentality’ and ‘consciousness’ arises as one thing and ceases as another by day and by night.
Although the commentaries, apparantly, do not see it like this, i believe this monkey simile refers to the untamed mind which attention is alternately caught by this and that. Scattered among the senses.
This describes the habitually clinging mind. Or mind with clinging. It unvoluntairy gets caught by this visual, that idea, this sound, that feeling, this smell, that emotion etc.
But the sutta’s also describe the mind as stable such as in AN4.24
"Thus, bhikkhus, being ever stable among things seen, heard, sensed, and cognized, the Tathagata is a stable one. And, I say, there is no stable one mote excellent or sublime than that stable one."
Amid those who are self-constrained, the Stable One
would not posit as categorically true or false
anything seen, heard, or sensed,
clung to and considered truth by others
Since they have already seen this dart
to which people cling and adhere,
[saying] “I know, I see, it is just so”
the Tathagatas cling to nothing.
Cling to nothing…comes with stability. If mind would be fundamentally unstable how can we ever arrive at stability? If there is no ground for stability or peace, then becoming stable would even mean that we become more deluded about how things really are, right? But i believe the Buddha teaches that there is a real ground for stability.
The mind is also described as something detached from the 5 khandha’s and as without boundaries, such as in AN10.81:
''Bahuna, it is because the Tathagata is released, detached, and emancipated from ten things that he dwells with a mind free from boundaries. What ten? (1) It is because the Tathagata is released, detached, and emancipated from form that he dwells with a mind free from boundaries. (2)-(5) It is because the Tathagata is released, detached, and emancipated from feeling . . . perception . … volitional activities . . . consciousness that he dwells with a mind free from boundaries. (6)-(10) It is because the Tathagata is released, detached, and emancipated from birth . . . old age . . . death . . . suffering . . . defilements that he dwells with a mind free from boundaries.
So, one can say that clinging mind. or mind with clinging, lives with boundaries and is unstable, but the mind without clinging is without boundaries and is experienced as stable.
The mind is also descibed in terms of being stilled and empty, and as with formations and, as it were full. One can abide in the essential emptiness of the mind (Mn121) which is said to be very peaceful. In the sense the mind can also be burdened and unburdened.
Mind has also an aspect of clear light or clarity. Which can also become part of someones practice:
"And what is the development of concentration that leads to obtaining knowledge and vision?7 Here, a bhikkhu attends to the perception of light; he focuses on the perception of day thus: 'As by day, so at night; as at night, so by day. Thus, with a mind that is open and uncovered, he develops a mind imbued with luminosity. This is the development of concentration that* *leads to obtaining knowledge and vision (AN4.41)
This also describes mind as open and uncovered. Mind can also be closed and covered.
Especially later buddhist have emphasized that ignorance in fact comes down to a misunderstanding of the nature of mind. Its essential emptiness is perceived in a distorted way as an ego or self that knows. Its lack of boundaries or openess is misunderstood and distorted into a dual world of a perceiver and perceived (subject and object). This seeminlgy dual nature of mind gives rise to emotions, like, dislike, indifference. Habitual patterns strenghten. A endless wheel.
So, this whole endless carreer in samsara relies on distortion, not seeing things as they really are, especially the nature of mind.