God is in form. He is in human like form. All the religious scriptures of major religions describe God as having human form. God is not formless.
Many ignorant souls describe God as "light". Light always has a source. You can't have light (formless) without a source (in form). Likewise God is in form and the light emanating from His body is formless.
Vedas clearly describe that God has a form / body
Yajurved Adhyay 5, Mantra 1 and Yajurved Adhyay 1 Mantra 15 use the words अग्नेतनुअसि - “Agne TanuH Asi | Vishnve Tva Somasya Tanur' Asi" which means that God in in form. Read full Ved Mantras. See video below for full details and debate with Arya Samaj.
In Gita (Shrimad Bhagavad Gita) Adhyay 11, Arjun is clearly describing the form of God he is seeing in front of his eyes as having arms, head, body, eyes, etc. The speaker of Bhagavad Gita further says that the form of mine that you have seen can never be seen by anyone else by any means. This does mean that God speaking Bhagavad Gita showed his form to Arjun by his own grace which is not possible to be seen by any means. This proves that God has a form.
Guru Nanak Dev Ji obtained True Naam (Satnaam) from a Complete Guru whom he met on the banks of River Bein who took Guru Nanak Dev Ji to Sachkhand (Satlok). Guru Nanak Dev Ji has sung the glory of a True Guru in His Bani in Shri Guru Granth Sahib on numerous occasions and have urged people to find a True Guru (Complete Guru) in order to achieve salvation.
Guru Nanak Dev Ji considered God as formless (nirankaar) prior to seeing God in Sachkhand but after seeing the Supreme God in Sachkhand, Guru Nanak Dev ji described the form of that Supreme God in great detail in his bani.
ਮਲਾਰ ਮਹਲਾ ੧ ॥ Page 1257, Shri Guru Granth Sahib
ਬਾਗੇ ਕਾਪੜ ਬੋਲੈ ਬੈਣ ॥
You wear white clothes, and speak sweet words.
ਲੰਮਾ ਨਕੁ ਕਾਲੇ ਤੇਰੇ ਨੈਣ ॥
Your nose is sharp, and your eyes are black.
Guru Nanak Dev Ji is seeing and addressing the Supreme God and is describing Him very beautifully and is clearly saying that you are wearing white clothes and you have a beautiful nose and black eyes.
ਕਬਹੂੰ ਸਾਹਿਬੁ ਦੇਖਿਆ ਭੈਣ ॥੧॥
Have you ever seen your Lord and Master, O sister? ||1||
बागे कापड़ बोलै बैण ॥
लमा नकु काले तेरे नैण ॥
कबहूं साहिबु देखिआ भैण ॥१॥
ऊडां ऊडि चड़ां असमानि ॥
साहिब सम्रिथ तेरै ताणि ॥
जलि थलि डूंगरि देखां तीर ॥
थान थनंतरि साहिबु बीर ॥२॥
जिनि तनु साजि दीए नालि ख्मभ ॥
अति त्रिसना उडणै की डंझ ॥
नदरि करे तां बंधां धीर ॥
जिउ वेखाले तिउ वेखां बीर ॥३॥
न इहु तनु जाइगा न जाहिगे ख्मभ ॥
पउणै पाणी अगनी का सनबंध ॥
नानक करमु होवै जपीऐ करि गुरु पीरु ॥
सचि समावै एहु सरीरु ॥४॥४॥९॥
You wear white clothes, and speak sweet words. Your nose is sharp, and your eyes are black. Have you ever seen your Lord and Master, O sister? ||1|| I fly and soar, and ascend to the heavens. By Your power, O my All-powerful Lord and Master. I see Him in the water, on the land, in the mountains, on the river-banks, in all places and interspaces, O brother. ||2|| He fashioned the body, and gave it wings; He gave it great thirst and desire to fly. When He bestows His Glance of Grace, I am comforted and consoled. As He makes me see, so do I see, O brother. ||3|| Neither this body, nor its wings, shall go to the world hereafter. It is a fusion of air, water and fire. O Nanak, if it is in the mortal's karma, then he meditates on the Lord, with the Guru as his Spiritual Teacher. This body is absorbed in the Truth. ||4||4||9||
ਵਡਾ ਸਾਹਿਬੁ ਹੈ ਆਪਿ ਅਲਖ ਅਪਾਰਾ ॥੬॥
वडा साहिबु है आपि अलख अपारा ॥६॥
The Great Lord Master is unfathomable and infinite. ||6||
ਤੇਰੇ ਬੰਕੇ ਲੋਇਣ ਦੰਤ ਰੀਸਾਲਾ ॥
तेरे बंके लोइण दंत रीसाला ॥
Your eyes are so beautiful, and Your teeth are delightful.
ਸੋਹਣੇ ਨਕ ਜਿਨ ਲੰਮੜੇ ਵਾਲਾ ॥
सोहणे नक जिन लमड़े वाला ॥
Your nose is so graceful, and Your hair is so long.
ਕੰਚਨ ਕਾਇਆ ਸੁਇਨੇ ਕੀ ਢਾਲਾ ॥
कंचन काइआ सुइने की ढाला ॥
Your body is so precious, cast in gold.
ਸੋਵੰਨ ਢਾਲਾ ਕ੍ਰਿਸਨ ਮਾਲਾ ਜਪਹੁ ਤੁਸੀ ਸਹੇਲੀਹੋ ॥
सोवंन ढाला क्रिसन माला जपहु तुसी सहेलीहो ॥
His body is cast in gold, and He wears Krishna's mala; meditate on Him, O sisters.
ਜਮ ਦੁਆਰਿ ਨ ਹੋਹੁ ਖੜੀਆ ਸਿਖ ਸੁਣਹੁ ਮਹੇਲੀਹੋ ॥
जम दुआरि न होहु खड़ीआ सिख सुणहु महेलीहो ॥
You shall not have to stand at Death's door, O sisters, if you listen to these teachings.
ਹੰਸ ਹੰਸਾ ਬਗ ਬਗਾ ਲਹੈ ਮਨ ਕੀ ਜਾਲਾ ॥
हंस हंसा बग बगा लहै मन की जाला ॥
From a crane, you shall be transformed into a swan, and the filth of your mind shall be removed.
ਬੰਕੇ ਲੋਇਣ ਦੰਤ ਰੀਸਾਲਾ ॥੭॥
बंके लोइण दंत रीसाला ॥७॥
Your eyes are so beautiful, and Your teeth are delightful. ||7||
ਤੇਰੀ ਚਾਲ ਸੁਹਾਵੀ ਮਧੁਰਾੜੀ ਬਾਣੀ ॥
तेरी चाल सुहावी मधुराड़ी बाणी ॥
Your walk is so graceful, and Your speech is so sweet.
ਕੁਹਕਨਿ ਕੋਕਿਲਾ ਤਰਲ ਜੁਆਣੀ ॥
कुहकनि कोकिला तरल जुआणी ॥
You coo like a songbird, and your youthful beauty is alluring.
ਤਰਲਾ ਜੁਆਣੀ ਆਪਿ ਭਾਣੀ ਇਛ ਮਨ ਕੀ ਪੂਰੀਏ ॥
तरला जुआणी आपि भाणी इछ मन की पूरीए ॥
Your youthful beauty is so alluring; it pleases You, and it fulfills the heart's desires.
ਸਾਰੰਗ ਜਿਉ ਪਗੁ ਧਰੈ ਠਿਮਿ ਠਿਮਿ ਆਪਿ ਆਪੁ ਸੰਧੂਰਏ ॥
सारंग जिउ पगु धरै ठिमि ठिमि आपि आपु संधूरए ॥
Like an elephant, You step with Your Feet so carefully; You are satisfied with Yourself.
ਸ੍ਰੀਰੰਗ ਰਾਤੀ ਫਿਰੈ ਮਾਤੀ ਉਦਕੁ ਗੰਗਾ ਵਾਣੀ ॥
स्रीरंग राती फिरै माती उदकु गंगा वाणी ॥
She who is imbued with the Love of such a Great Lord, flows intoxicated, like the waters of the Ganges.
ਬਿਨਵੰਤਿ ਨਾਨਕੁ ਦਾਸੁ ਹਰਿ ਕਾ ਤੇਰੀ ਚਾਲ ਸੁਹਾਵੀ ਮਧੁਰਾੜੀ ਬਾਣੀ ॥੮॥੨॥
बिनवंति नानकु दासु हरि का तेरी चाल सुहावी मधुराड़ी बाणी ॥८॥२॥
Prays Nanak, I am Your slave, O Lord; Your walk is so graceful, and Your speech is so sweet. ||8||2||
Bible describes in genesis on the sixth day of creation that "God created man like Himself", in his own likeness.
26 Then God said, "And now we will make human beings; they will be like us and resemble us
27 So God created human beings, making them to be like himself. He created them male and female
In Surat Furqan 25, Aayat 52-59 describes the creation of nature in 7 days which matches with Bible and then says that God took rest on the seventh day and sat on his throne.
God can only sit on His throne if He is in form. What sort of a throne is a formless God going to sit on?