Allah has Himself explained ‘Islam’ in the Qur’an, which can be learned through Tasreef. Tasreef is the Qur'anic process where words and verses in one part of the Qur’an explain or provide deeper understanding of the words and verses in other parts of the Book. Please see the following verse:
3:83 Do they seek other than the DEEN of Allah (GOD in Arabic), when all things in the heavens and the earth, willingly and unwillingly submit (aslama) to Him, and to Him they will be returned.
According to the above verse (3:83), everything in the heavens and the earth submit to Allah (aslama). In other words, everything is Muslim. Note the word ‘aslama’ and ‘Deen’.
13:15 And all things in the heavens and the earth, willingly and unwillingly bow to Him (in obedience) (yasjudu) ……
In 13:15, the word ‘yasjudu’ has been used instead of ‘aslama’. In other words, ‘aslama’ in 3:83 has been used quite synonymously to ‘yasjudu’ in 13:15. Islam means submission. Sajda means bowing or prostrating in submissiveness or submission. Obviously, everything in the heavens and the earth do not prostrate as humans do physically by putting their foreheads on the ground but this means the submissiveness and obedience of these things to Allah’s Amr or Command or Law. It is a fact that every object and every phenomenon in the universe is governed by certain laws. It may be the case that science has not discovered so far all the laws that govern everything but there is nothing that does not follow a law. What they call ‘natural laws’, Allah clarifies to them that these are His Laws.
Allah has further explained in the Quran the nature of Islam or submission of everything to Allah. In the Quran, Allah say:
22:18 Don't you see that all things and beings in the heavens and in the earth, the sun and the moon, and the stars and the mountains, and the trees, and the animals, and a great many human beings bow themselves to Allah (in submissiveness and obedience) (yasjudu)? …………
16:49-50 Behold, before Allah, bows in submission all that is in the heavens and all that is in the earth, whether living beings or the angels, for none are arrogant. They all fear their Lord, High above them, and they do all that they are commanded (Yumaroon).
From the above, it can be seen that the submission or bowing or prostrating of things to Allah in submissiveness means ‘to do what He commands’. This is what the Islam is, i.e. doing what Allah commands.
Allah created everything and then gave it guidance of the way that it should follow.
20:50 …, "Our Lord is He who creates and shapes everything, grants it its constitution and guides it aright."
For example, Allah sent wahi or command to Heavens to assign them their function.
41:12 And He it is Who ordained that they become seven Heavens in two stages and assigned to each heaven its function….
Similarly, wahi and command to the Earth:
99:5 For your Lord would send His Command to her (the earth)
Everything in the heaven and the earth is striving to carry out the tasks assigned by Allah. Everything knows its SALAAT and TASBEEH.
24:41 Do you not realize that Allah, It is He Whose assigned tasks all beings in the heavens and the earth carry out, and the birds, with their wings outspread, as they fly in columns. All of them know their SALAT and TASBEEH (mission and strife). Allah is Aware of what they do.
According to 24:41, everything is doing TASBEEH. The verse 24:41 ends with the words, ‘Allah is aware of what they do’, clarifying that TASBEEH is not something to be said or recited but something to be done.
2:116 ….. Nay, unto Him belongs all that is in the heavens and the earth. Everything is wholeheartedly subservient/obedient to Him.
As can be seen from the above given verses, Allah created everything and gave it guidance to the way it should follow. Everything knows its SALAAT and TASBEEH, its function and role. Everything is obedient/subservient to Allah and does exactly what Allah commanded to them. This is their Islam or submission to Allah.
The difference between their submission and man’s submission is that these things are bound to follow Allah’s laws willingly or unwillingly [3:83, 13:15]. They do not have any choice. The Sun does not have any choice to change its course. The stars do not have any choice to move to any position other that the ordained, and so on. All are whole-heartedly obedient to Allah’s commands [2:116]. But man has not been created to be obedient by default but he is commanded to do so by choice [2:238]. Whatever is in the heavens and the earth submits to Allah’s commands willingly or unwilling [3:83]. But human beings have choice. Whoever among them submits his whole self entirely to Allah, will have his reward with his Lord [2:112].
It follows from the above that
Everything in the Heavens and the earth submits to Allah. Their Islam or submission is that they all are wholeheartedly obedient/subservient to Allah and do what they are commanded.
Man is also required to do the same but by choice. He is required to be Al-Muslim i.e. to submit himself to Allah which means being wholeheartedly obedient to Allah and doing what He has commanded.
Submission in Islam means submission to God and not submission to Muslims or their Khalifa or leader. Submission is willingly to God, Muhammad (PBUH) was not able to guide all his families to Islam. In fact one of the worst enemies of Muhammad and Islam was one of his own uncles (Abi-Lahab), while most of his uncles and family became Muslims. Another uncle who would protect him most was Abi-Talab and Muhammad love him much however was not able to guide him to Islam (God said to Muhammad in the Quran " you do not guide whom you love but God guide who he will to guide". Thus guidance is totally is in God hands (depending mostly in man sincerity) we as Muslims to explain well the Islam to all humans. In the time of tribulation we are in now guidance to Islam is difficult given the craziness around us and corruption of humans in everything even God's messages. As well it is easy to guide people since there is no other way to salvation but to follow God and submit to him and follow the teachings of the great prophets Jesus and Muhammad peace be upon them both.